A solitary pulmonary nodule (SPN) is defined as a single discrete pulmonary opacity that is surrounded by normal lung tissue and is not associated with adenopathy or atelectasis. The finding of an SPN on a chest radiograph is a diagnostic dilemma often faced by many clinicians. The differential diagnosis may be broad but implications rest on whether the lesion is benign or malignant.
Radiographically, a nodule is defined as a lesion smaller than 3 cm. Anything larger than 3 cm is termed a mass.
Clinical Details: Most SPNs are asymptomatic. The goal of investigating an SPN is to differentiate a benign lesion from a malignant lesion as soon and as accurately as possible.
Important features in the patient history include the following:
- Age – Risk of malignancy increases with age
- Risk of 3% at age 35-39 years
- Risk of 15% at age 40-49 years
- Risk of 43% at age 50-59 years
- Risk of greater than 50% in patients older than 60 years
- Smoking history
- Prior history of malignancy
- Travel history – Travel to areas with endemic mycosis (eg, histoplasmosis, coccidioidomycosis, blastomycosis) or a high prevalence of tuberculosis
- Occupational risk factors for malignancy – Exposure to asbestos, radon, nickel, chromium, vinyl chloride, and polycyclic hydrocarbons
- Previous history of tuberculosis or pulmonary mycosis
- Rounded atelectasis
The term atelectasis, defined as diminished lung volume, is derived from the Greek words ateles and ektasis, which mean incomplete expansion. Atelectasis may affect all or part of a lung, and it is one of the most common radiographic abnormalities. Recognizing atelectasis on a chest radiograph is important because a sinister underlying pathology may be present. Several types of atelectasis have been described; each has a unique radiographic pattern. Atelectasis can be categorized as obstructive or nonobstructive.
In cases of rounded atelectasis, segmental or subsegmental atelectasis occurs secondary to visceral pleural thickening and entrapment of the lung tissue.
Rounded atelectasis manifests as a subpleural mass, and bronchovascular structures radiate out of the mass toward the hilum. An associated parietal pleural plaque may be present. The swirl appearance of bronchovascular shadows is called the comet-tail sign and establishes the diagnosis
Pulmonary aspergillosis is a spectrum of mycotic diseases caused by Aspergillus species, usually Aspergillus fumigatus. This intensely antigenic and ubiquitous soil fungus is commonly found in the sputum of healthy individuals. However, in susceptible hosts, its ability to invade the arteries and veins facilitates its hematogenous spread.
The development of disease and its histologic, clinical, and radiologic manifestations depend on the virulence and number of spores inhaled and, more importantly, on the patient’s immune status.
Pulmonary aspergillosis may take any of 4 forms:
- Allergic bronchopulmonary aspergillosis (ABPA) is caused by a hypersensitivity reaction to the fungus and most commonly occurs in those with asthma.
- Saprophytic aspergillosis, or aspergilloma, is the most common form. This form is noninvasive and involves colonization of preexisting cavities.
- Chronic necrotizing aspergillosis, also called airway-invasive or semi-invasive aspergillosis, is a chronic cavitary pneumonic illness that often affect patients with preexisting chronic lung disease.
- Angioinvasive aspergillosis affects immunocompromised patients and is often fatal.
ABPA can be staged by using the following clinical and radiologic criteria:
- Stage I – Acute presentation with 6 of the 8 primary diagnostic criteria listed above
- Stage II – Resolving pulmonary infiltrates with decreasing IgE levels leading to remission
- Stage III – Recurrence of acute symptoms after a period of remission
- Stage IV – Steroid dependency
- Stage V – Irreversible lung damage leading to fibrosis
Findings: In ABPA, chest radiographic appearances include the following: (1) fleeting alveolar subsegmental or lobar infiltrates, which are usually bilateral (65%) and predominant in the upper lobes (50%); (2) central 1-2-cm ring shadows that represent varicose or cystic bronchiectasis; and (3) tram-link bronchial walls due to edema. The second-order bronchi may become plugged with mucus, and they may be visible as 2.5-6-com long V- or Y-shaped branching tubular opacities that may grow over time and persist for months; this is the so-called finger-in-glove sign.
Other features include lobar consolidation, atelectasis, postobstructive pneumonia, cavitation, air trapping, and parenchymal scarring or fibrosis, all of which are more pronounced in the upper lobes. Focal pleural thickening is also reported. Occasionally, mycetomas develop in ectatic bronchi.
The characteristic chest X-ray appearance of an aspergilloma is that of a round or oval mass with the opacity of that of a soft-tissue mass. Often, an adjacent crescent-shaped air space (ie, the air-crescent sign) separates the fungal ball from the cavity wall. The mycetoma may rarely contain amorphous or rimlike calcification. The fungal ball is usually mobile and moves when the patient changes position. Often, extensive adjacent apical pleural thickening may be present; this finding may herald the development of the mycetoma.
The radiologic manifestations of chronic necrotizing aspergillosis include unilateral or bilateral segmental areas of consolidation that are predominant in the upper lobes; frequently, these progress to cavitation. Pleural thickening also is a recognized feature.
The most common chest radiographic appearance of invasive aspergillosis is that of patchy areas of consolidation, which progress despite the use of broad-spectrum antibiotics. Multiple nodules and peripheral wedged-shaped lesions due to hemorrhagic infarcts are also observed as the disease progresses. These frequently become cavitated, and an air-crescent sign that mimics mycetoma may also be observed.
Blastomyces dermatitidis is a thermally dimorphic fungus that causes the systemic pyogranulomatous disease termed blastomycosis. Blastomycosis is the least common of the endemic systemic mycoses; the other more common mycoses include histoplasmosis and coccidioidomycosis. Lungs, and to a lesser extent, skin and bone, are the most common organs involved with this fungus. Hematogenous dissemination can occur.
Pathophysiology: Analysis of sporadic cases indicates that middle-aged men with outdoor occupations that exposed them to soil are at greatest risk for blastomycosis. Exposure to soil, whether at work or at play, appears to be the common link in reports of sporadic disease and outbreaks. The disease occurs more commonly in wooded areas and in hunters.
The respiratory system is considered the portal of infection. After inhalation of the conidia, neutrophils are the first cells recruited to the sites of infection, followed by lymphocytes. A reaction to the infection results in granuloma formation with central microabscesses (termed pyogranuloma) but does not result in caseation as occurs in histoplasmosis or tuberculosis.
Chest radiographs usually reveal focal lung opacities in the upper lobes (in 25-75% of patients), often nodular in character. In adults, the upper lobes are affected more frequently than the lower lobes with a ratio of approximately 2:1. In children, opacities most commonly involve the lower lobes. Lung opacities can be patchy or confluent and subsegmental, segmental, or nonsegmental. Radiographically, the appearance is similar to that seen with community acquired pneumonia, but slow improvement, lack of change, or even progression of disease over time should raise the possibility of granulomatous infection.
The next most common radiographic presentation (in as many as 30% of patients) is a focal discrete mass, either single or multiple. The mass is usually well circumscribed, variable in size, and can occasionally contain air-bronchograms. When solitary, it can mimic primary carcinoma, especially when associated with unilateral lymph node enlargement or bone destruction.
In contrast to histoplasmosis, hilar and mediastinal adenopathy and calcification are uncommon (10-20%).
Bronchogenic cysts are congenital in nature. They are part of a spectrum of congenital abnormalities of the lung including pulmonary sequestration, congenital cystic adenomatoid malformation, and congenital lobar hyperinflation (emphysema).
Pathophysiology: Bronchogenic cysts develop from an abnormal budding of the ventral foregut between the 26th and 40th week of gestation. As such, they are often more appropriately termed foregut duplication cysts.
Findings: Mediastinal cysts are visualized as a mediastinal mass on conventional radiographs. Intrapulmonary cysts usually present as a solitary pulmonary nodule unless the cyst contains air.
Infection with Coccidioides immitis, a soil-inhabiting fungus, causes an illness in humans called coccidioidomycosis.
C immitis is a fungus that thrives in soil, and its growth occurs in either of 2 phases: the mycelial arthrospore phase in the soil and the spherule endospore phase in infected tissues. The mycelia are the least infectious but the hyphae develop into arthrospores that become airborne and are highly infectious.
After the organism is inhaled into the lungs, the arthrospore develops into a thick-walled spherule filled with endospores. Once released, each endospore can start the development of a new spherule and the infection in the host progresses. Coccidioidomycosis is not known to transmit from person to person.
Primary pulmonary coccidioidomycosis
The thoracic manifestations of primary infection include parenchymal disease, intrathoracic adenopathy, and pleural effusion.
Parenchymal consolidation is the most common manifestation seen in 75% of patients. The segmental or subsegmental consolidation is single or multiple, usually unilateral and in perihilar or basal distribution. These may resolve spontaneously within 1-2 weeks.
In 20% of patients, nodular lung disease is seen. The nodules frequently are well defined, simulating metastasis, or they may have ill-defined margins. They have a parahilar and lower-lobe distribution, and they are 5-25 mm in size.
In approximately 20% of patients, hilar adenopathy is present. This is usually unilateral and concomitant with parenchymal lesions. Mediastinal adenopathy is seen with severe and prolonged infection and is associated with a higher risk for dissemination.
Persistent or chronic pulmonary coccidioidomycosis
Approximately 5% may develop a persistent pulmonary disease when the primary disease is present for longer than 6 weeks. This disease may include persistent pneumonia with or without adenopathy, nodules and cavities, pleural disease, bronchiectasis, empyema, or calcifications. Only 25% of patients with chronic changes have a history suggestive of an antecedent acute primary pulmonary coccidioidal illness.
Pulmonary nodules from coccidioidomycosis are the most common radiographic findings in persistent pulmonary infection. Nodular lesions (coccidioidomas) represent localized foci of incompletely resolved consolidation. Nodules may also form from filling in of a cavity. Nodules are usually well circumscribed and round, with average size of 1.5-2 cm. They are usually single and tend to occur in the periphery of middle and upper lung zones. In contrast to those in tuberculosis, these nodules may develop in the anterior segment of an upper lobe. These nodules may remain stable for months and eventually regress; only rarely is slow growth is observed.
Cavities may develop as a result of necrosis in an area of pneumonia or excavation of a nodule. Those formed by means of excavation have been reported in 10-15% of patients. Usually, these appear singly and are located in the upper lobes. They may have thin or thick walls; thin-walled cavities have a tendency to change in size, which possibly reflects check-valve communication with the bronchial tree.
A rapid change in the size of a cavity suggests coccidioidal infection rather than any other granulomatous infection. A single asymptomatic thin-walled cavity is probably more common than other types. Most of the cavities close spontaneously in 2 years, although some may remain stable in size, but they are not known to produce disseminated disease. Rarely, these cavities may be colonized by Aspergillus organisms and develop a mycetoma. The cavities may wax and wane over the years. A subpleural cavity may also break down into the pleural cavity, causing a pneumothorax, pyopneumothorax, or bronchopleural fistula.
Histoplasmosis is the most common of the endemic mycoses and a major cause of morbidity and mortality in patients living in endemic areas. Histoplasma capsulatum first was described in 1905 by Samuel Darling, a US Army pathologist stationed in Panama. Darling examined visceral tissues and bone marrow from a young man from Martinique whose death originally was attributed to miliary tuberculosis. The organism initially was described as protozoal. Because it lacked a kinetoplast, Darling assumed that it was a different species of Leishmania. He termed it H capsulatum.
Findings: Radiographic findings depend primarily on the type of presentations and the immune status of the host.
Chest radiographic findings are normal in most patients. A solitary pulmonary nodule is a frequent finding on chest radiographs of the patient with asymptomatic primary infection. These nodules vary from a few millimeters to several centimeters. Most of these nodules have well-defined margins and central, laminar, or diffuse calcification patterns. Interestingly, some nodules can slowly enlarge because of continued elaboration of collagen at the periphery of the lesion, thus can be difficult to distinguish from malignancy.
As many as 10-25% of patients with asymptomatic infection develop single or multiple poorly defined areas of airspace consolidation and/or nodules, with or without hilar lymph node enlargement. Enlarged lymph nodes often are seen after an asymptomatic infection. Adenopathy is frequently seen with lung parenchymal abnormalities and often contain calcification. This calcification occasionally may be seen on CT only. Patients with noncalcified mediastinal adenopathy need to be distinguished from sarcoidosis, lymphoma, and metastasis. Enlarged lymph nodes can cause significant bronchial or tracheal compression or obstruction and may cause esophageal obstruction. As a consequence of airway obstruction, atelectasis, collapse, and obstructive pneumonitis can develop.
Lung cancer is divided into 2 categories: small-cell lung cancer and non–small cell lung cancer.
Approximately 20% of malignant tumors of the lung are due to small cell carcinoma. At presentation, small cell lung cancer is almost always metastatic to the mediastinal lymph nodes or distantly; therefore, the treatment is combination chemotherapy.
Non–small cell cancer requires meticulous staging, because the treatment and prognosis vary widely depending on the stage. In non–small cell lung cancer, surgical resection offers patients the best chance for survival.
Pathophysiology: Bronchogenic carcinoma is the most common cancer and the most common cause of cancer-related death in both men and women. Risk factors for lung cancer include the following:
- Cigarette smoking
- Exposure to asbestos
- History of interstitial lung disease
- Exposure to toxic agentsExposure to uranium or radon
- Prior lung cancer
- Lung disease
- HIV infection
Squamous cell carcinoma
Squamous cell carcinoma accounts for 30-40% of cases of bronchogenic carcinoma, and it has a strong association with smoking. The lesion is usually located centrally, and among all bronchogenic carcinomas, it is most likely to cavitate. Squamous cell carcinomas grow intraluminally and are least likely to metastasize distantly (<20% of cases at presentation). The mode of spread is direct extension to the local lymph nodes. Squamous cell carcinomas are commonly associated with clubbing and hypertrophic osteoarthropathy. Ç
Adenocarcinoma occurs with a frequency of 30-40%, which has surpassed the incidence of squamous cell carcinoma. The lesion is located peripherally in approximately one half of cases, and it is associated with smoking. Adenocarcinoma may arise from a previous scar, it rarely cavitates, and an eccentric pattern of calcification may be evident. An early propensity is noted of metastases to the lymph nodes, pleura, adrenal glands, central nervous system (CNS), and bone.
Bronchoalveolar cell carcinoma
Bronchoalveolar cell carcinoma is a subtype of adenocarcinoma that accounts for as many as 5% of bronchogenic carcinomas.
Bronchoalveolar cell carcinoma is classified as mucinous and nonmucinous on the basis of histopathologic features. The mucinous variety is most common (80%) and arises from columnar mucous containing cells. The mucinous variety is likely to be multicentric, it occasionally appears with bronchorrhea, and it has a worse prognosis. The nonmucinous form arises from type II pneumocytes or Clara cells, it is more likely to be localized, and it has a better prognosis. Bronchoalveolar carcinoma may spread to other sites or the other lung by means of transbronchial spread called aerogenous spread. These tumors can also demonstrate growth along the pulmonary interstitium without destroying lung architecture. This is called lepidic growth. In comparison, both types of growth are associated with a worse prognosis.
Bronchoalveolar carcinoma may appear in a variety of ways, including a solitary pulmonary nodule (45%), multiple nodules (25%), and consolidation (30%). Presentation as a solitary pulmonary nodule is associated with the best prognosis. Nodules can be sharp or poorly defined, and they may be cavitated. In 30% of patients, an associated pleural effusion is noted, as well as hilar or mediastinal lymphadenopathy.
Large cell carcinoma
Large cell carcinomas account for only 5-10% of bronchogenic carcinomas and are strongly associated with cigarette smoking. The lesion occurs peripherally and grows rapidly, with early metastases and a poor outcome. A subtype of large cell carcinoma is giant cell carcinoma. This is highly malignant and associated with a poor prognosis.
Findings: On chest radiography, the findings of non–small cell lung carcinomas are varied and considered in the differential diagnosis of many disorders. The most common findings are described below.
Central bronchogenic carcinomas manifest added opacity in the hilar region. In the early stage, the tumor may fill the lateral concavity of the hilar shadow, and in the advanced stage, all hilar structures are obliterated. Infiltration of lymphatics with bronchogenic carcinomas may be demonstrated as linear opacities radiating from the hilar mass into the lung periphery.
Solitary pulmonary nodule
A solitary pulmonary nodule may be relatively well marginated and appears as a rounded lung opacity. Reportedly, a solitary pulmonary nodule is benign in as many as 60% of patients in some series. All patterns of calcification except eccentric or scattered punctate (stippled) calcification are associated with a benign lesion.
Other possible signs of malignancy include the following:
- Diameter more than 3 cm
- Ill-defined or spiculated margin
- Rigler notch sign (a notch on the nodule corresponding to the vascular supply)
- Radial striated markings at the nodular margin (termed corona radiata)
- Thick-walled cavity
- Eccentric calcification
An ill-defined homogeneous or patchy consolidation in a segmental or nonsegmental distribution may be an indication of bronchogenic carcinoma. Patients with these findings often are treated initially for pneumonia; the lack of response to antibiotic therapy suggests the diagnosis of a malignancy.
The opacity may contain air bronchograms and air alveolograms. This presentation is often seen with adenocarcinoma and bronchoalveolar carcinoma.Indirect signs of involvement of contiguous structures also may be found. Bronchogenic carcinoma may involve the surrounding thoracic structures, which often indicates that the tumor is not resectable. Findings include the following:
SCLC is categorized into 2 stages: limited disease and extensive disease. The disease is termed limited when it is confined to an area of the chest that can be encompassed by a single irradiation port; supraclavicular nodes may be included. The disease is called extensive when metastasis outside the thorax is present or when intrathoracic disease cannot be contained in a single irradiation port.
Findings: Chest radiographs may show unilateral hilar enlargement, increased hilar opacity, a perihilar mass, mediastinal mass, or a combination of these. Less commonly, SCLC may appear as a solitary pulmonary nodule.
Compression of the bronchi is relatively common in SCLC because of the central location of the tumor in most cases. About 30-50% of SCLCs show evidence of obstructive pneumonitis on the initial presentation. SCLC can appear as segmental or lobar atelectasis with or without an obvious hilar mass. The S sign of Golden is seen when a collapsed upper lobe forms a meniscus concave toward the hilum and when an enlarged hilar mass forms the convex meniscus of the S. Occasionally, endobronchial growth or bronchial compression may be appreciated as a bronchial cutoff or filling defect.
Thickening of the right paratracheal stripe may be an indication of right paratracheal lymphadenopathy. With massive subcarinal lymphadenopathy, widening of the carinal angle may occasionally be observed. Subtle changes of hilar asymmetry, increased opacity, a convex or lobulated outer hilar border, or any change from a previous radiograph should be viewed with suspicion.
First described in 1897, pulmonary arteriovenous malformation (PAVM) is an abnormal communication between the pulmonary artery and the pulmonary vein. PAVMs are usually congenital in origin; however, they may be acquired in a variety of conditions, such as hepatic cirrhosis, schistosomiasis, mitral stenosis, trauma, actinomycosis, and metastatic thyroid carcinoma.
After the initial description of telangiectasia and epistaxis by Henry Jules Rendu in 1896, Sir William Osler reported a family known to have hereditary hemorrhagic telangiectasia (HHT). In 1907, Frederick Weber described other manifestations of this disorder; since then, HHT has come to be known as Rendu-Osler-Weber syndrome. Approximately 70% of PAVMs are associated with HHT, and about 15-30% of individuals with HHT have a PAVM.
Findings: Chest radiography is recommended as the initial evaluation of patients with HHT. PAVM may well be an incidental finding on a chest radiograph. A common radiographic finding is a round or oval mass of uniform opacity. The opacity may have sharply defined borders with occasional lobulation. The mass is usually 1-5 cm, and linear shadows are adjacent to the opacity; these are the feeding vessels. PAVMs are commonly present in the lower lobes, and approximately one half of patients have 2-8 lesions.
Bronchial carcinoid tumors are rare, accounting for as many as 2.5% of all pulmonary neoplasms and for 12-15% of carcinoid tumors overall. They originate from the neurosecretory cells of bronchial mucosa and were previously classified as bronchial adenomas, a term no longer used. Bronchial carcinoids are now classed as low-grade malignant neoplasms because of their potential to cause local invasion, their tendency for local recurrence, and their occasional metastases to extrathoracic sites. Bronchial carcinoid tumors arise from Kulchitsky cells (argentaffin cells) within the bronchial mucosa. The predominant distribution of cells occurs at the bifurcation of the lobar bronchi. These cells are neurosecretory cells, which belong to the amine precursor uptake and decarboxylation (APUD) system. They have the capacity to synthesize serotonin (5-hydroxytryptamine), 5-hydroxytryptophan, ACTH, norepinephrine, bombesin, calcitonin, antidiuretic hormone (ADH), and bradykinin.
Findings: KCC I and KCC II (typical and atypical carcinoids) have similar radiographic appearances. CXRs are abnormal in most patients. In approximately 80% of cases, carcinoids arise centrally in the main, lobar, or segmental bronchi without any predilection for a particular bronchus/lobe. Radiographic findings include a hilar or perihilar mass abutting or narrowing a central airway or changes associated with an endobronchial tumor.
Because the tumors are slow growing, and ancillary findings due to bronchial obstruction may also be seen. These findings include atelectasis; bronchiectasis; pneumonitis; mucous impaction (bronchocele) of a distal bronchus; and, occasionally, distal abscess formation. However, a collateral drift may maintain aeration of the obstructed segments. The consequent hypoxia of the involved lung is sometimes seen as local vasoconstriction.
Mucoid impaction may be the only radiographic finding, and this is seen as a well-defined round, elliptical, or triangular opacity pointing toward the hilum. It is occasionally branching, looking like gloved fingers.
As many as 20% of bronchial carcinoids occur as a solitary pulmonary nodule. Overall, the tumors are usually well defined, lobulated, round or oval lesions sized 2-5 cm. Atypical carcinoids are more likely to be peripheral, and they tend to be larger. Eccentric calcification or ossification is rarely appreciated on CXRs, but it is present in 30% of biopsy specimens. Spiculation is rare, but when it is present, differentiation of this tumor from a bronchogenic carcinoma may be difficult. Multifocal disease is rarely seen. Although rare, sclerotic bone metastases are usually well seen on conventional radiographs.
Pulmonary metastases are common. They most frequently occur with tumors that have rich systemic venous drainage. Examples include renal cancers, bone sarcomas, choriocarcinomas, melanomas, testicular teratomas, and thyroid carcinomas. Most pulmonary metastases arise from common tumors such as breast, colorectal, prostate, bronchial, head and neck, and renal cancers. The detection of pulmonary metastases is crucial in the treatment of patients with cancer.
Pulmonary nodules are the most common manifestation of secondary neoplastic disease in the lungs. They are usually derived from tumor emboli arising from invasion of tumor capillaries. The tumor emboli drain via the systemic veins and pulmonary arteries. They subsequently lodge in the small pulmonary arteries or arterioles and extend into adjacent lung tissue. Pulmonary nodules are usually multiple, spherical, and variably sized. Metastases that occur via bronchial arteries, pulmonary lymphatics, transbronchial aspiration, and across the pleural cavity are less common.
Lymphangitis carcinomatosis is usually the result of hematogenous metastases to small pulmonary capillaries, with secondary invasion of peripheral pulmonary lymphatics. Retrograde extension from hilar or mediastinal nodes or direct invasion from diaphragmatic lymphatics is less common. Breast, lung, stomach, pancreas, and prostate cancers are the most common tumors that result in lymphangitis. Endobronchial metastases are rare, and they are associated with tumors of the breast, colon, and kidney, as well as sarcoma and melanoma.
- Incidence of Pulmonary Metastases According to Site
|Primary Tumor||Frequency at Presentation, %||Frequency at Autopsy, %|
|Testis, germ cell||12||70-80|
|Head and neck||5||15-40|
Findings: Standard CXR is usually the initial test in the detection of pulmonary metastases. More lesions are detected with a high-kilovoltage technique (>125 kV) than with the standard technique.
Patterns of disease
Pulmonary metastases are usually multiple. They vary in size from 3 mm to 15 cm or more. Nodules of the same size are believed to originate at the same time, in a single shower of emboli. Rarely, numerous tiny nodules mimic the pattern of miliary tuberculosis. Nodules are found most commonly in the outer third of the lungs, especially in the subpleural regions of the lower zones.
Nodules smaller than 2 cm are often round and have smooth margins. Larger nodules, especially metastatic adenocarcinoma, are frequently lobulated and have irregular margins. They may become confluent with adjacent masses, resulting in multinodular masses.
A pneumothorax associated with pulmonary metastases usually indicates that an osteosarcoma is the primary site. As many as 5% of these patients may have a pneumothorax, and this occurs more commonly during chemotherapy.
Hemorrhagic metastases, with a halo of hazy opacity, are most often seen in choriocarcinoma, but also occasionally appear with other vascular tumors such as angiosarcoma or renal cell carcinoma. Metastases from teratoma of the testis may show complete fibrosis or necrosis after chemotherapy. Thin-walled air cysts are present at the site of a treated metastasis (see Images 13-14). These air cysts contain no viable tumor.
Solitary pulmonary metastases are uncommon and account for 2-10% of all solitary nodules. The primary lesions that are more likely than others to produce solitary metastases include the following: carcinoma of the colon, especially that of the rectosigmoid area, which accounts for one third of cases; osteosarcoma; carcinoma of the kidney, testicle, or breast; and malignant melanoma.
Usually, no reliable features that distinguish a solitary metastatic nodule from a primary pulmonary carcinoma are demonstrated on CXR or CT images. On HRCT scans, approximately one half of metastatic nodules demonstrate irregular margins. They may be round or oval, or they may have lobulated margins. Irregular margins with spiculation may be caused by a desmoplastic reaction or tumor infiltration into the adjacent lymphatics or bronchovascular margin.
The distinction between a new primary tumor and metastasis has important prognostic and therapeutic implications. Resection of a solitary metastasis may be beneficial. The interval between the appearance of the initial tumor and the appearance of the solitary nodule is also relevant.
Although any neoplasm can cause lymphangitic spread, tumors most commonly originate in the breast, stomach, pancreas, or prostate. They are also caused by primary pulmonary carcinoma, especially small cell carcinoma and adenocarcinoma. Lymphangitic spread is present in 35% of autopsies of patients with solid tumors. Associated pleural involvement is common.
Microscopically, malignant cells are readily seen in lymphatic cells and interlobular septa. Edema or a desmoplastic reaction can contribute to interstitial thickening. The typical radiographic pattern consists of thickened interlobular septa (5-10 mm or smaller) and bronchovascular markings of irregular contour. The pattern is more obvious in the lower zones. A
Tuberculosis is an infectious disease that has been known for centuries. Traditionally, the term tuberculosis has been used to indicate infections caused by Mycobacterium tuberculosis and Mycobacterium bovis; however, a multitude of mycobacteria are recognized.
Tuberculosis may involve multiple organs such as the lung, liver, spleen, kidney, brain, and bone. In endemic regions, the normal host immune response may be sufficient to contain the infection and prevent clinical presentation. Uncontrolled or uncontained infection may result in great morbidity and mortality
Pulmonary imaging findings in individuals with primary tuberculosis are nonspecific. Atelectasis may occur in primary pulmonary tuberculosis, often as a consequence of tuberculous airway involvement. Parenchymal consolidation may be observed.
Although consolidation may occur in any segment or lobe or in multiple segments or lobes, the disease has a predilection for the lower lobes, for the middle lobe and lingula, and for the anterior segments of the upper lobes.
The lung opacity tends to become rounded with healing, and it continues to shrink until only a small nodule remains. Subsequently, the nodule may become calcified or ossified, resulting in a calcified granuloma. Note that although a granuloma may calcify, this does not necessarily reflect an absence of bacilli. The organisms may remain quiescent within this nodule, serving as a possible source for reactivated of disease.
The findings of reactivation tuberculosis typically become radiographically apparent within 2 years of the initial infection. Postprimary tuberculosis may have any of a number of parenchymal manifestations including the following: Patchy or confluent airspace opacities are opacities that involve the apical and posterior segments of the upper lobes and the superior segments of the lower lobes.
Tuberculomas are rounded discrete nodules that are known to harbor bacilli. They may be present in primary or postprimary tuberculosis and radiographically appear as discrete nodules, typically within the upper lobes. Tuberculomas may calcify. Satellite lesions (ie, small discrete nodules in the vicinity of the tuberculoma) are present in as many as 90% of patients.
Pancoast tumors are neoplasms of pulmonary origin located at the apical pleuropulmonary groove (superior sulcus). By direct extension, they typically involve the lower trunks of the brachial plexus, intercostal nerves, stellate ganglion, adjacent ribs, and vertebrae.
Findings: Posteroanterior (PA) chest radiographs show unilateral apical opacity or just asymmetry of the apices of greater than 5 mm. Local rib destruction can sometimes be observed. Lordotic chest views can be beneficial, but the findings can also be misleading.
Sarcoidosis almost always affects the respiratory system. Most patients present with the classic combination of bilateral hilar lymphadenopathy, parenchymal disease of the lung, and eye or skin lesions; however, virtually any organ in the body may be involved. At diagnosis, about 50% of patients are asymptomatic, 25% complain of cough or dyspnea, and 25% have or develop eye symptoms or skin lesions (eg, such as erythema nodosum, lupus pernio, plaques or scars).
Bilateral hilar lymphadenopathy is the most common radiographic finding. Other radiographic findings include interstitial lung disease; occasional calcification of affected lymph nodes; and rarely, pleural effusions and thickening.
Characteristic radiographic appearances are reported in approximately 60-70% of patients with sarcoidosis. The radiographic changes in thoracic sarcoidosis is usefully classified into 5 groups or stages:
- Stage 0 – No demonstrable abnormality
- Stage 1 – Hilar and mediastinal lymph node enlargement not associated with pulmonary abnormality
- Stage 2 – Hilar and mediastinal lymph node enlargement associated with pulmonary abnormality
- Stage 3 – Diffuse pulmonary disease not associated with nodal enlargement
- Stage 4 – Pulmonary fibrosis
Hilar and/or mediastinal lymphadenopathy is found in the majority of patients with sarcoidosis; this is the most common finding. The most frequent presentation is bilateral hilar and right paratracheal lymphadenopathy. Left paratracheal and aortopulmonary window lymph nodes are also frequently involved, but they may be difficult to detect on a standard posteroanterior (PA) chest radiograph.
Atypical lymphadenopathy may rarely affect the paratracheal, subcarinal, aortopulmonary window, and retroazygous nodes unaccompanied by hilar lymphadenopathy. Radiographic evidence of anterior mediastinal adenopathy is seen in less than 10% of cases. The posterior mediastinum is least commonly involved. The findings of isolated lymphadenopathy in the anterior or posterior mediastinal compartments should raise the possibility diagnoses other than sarcoidosis. Isolated unilateral hilar lymphadenopathy is an unusual manifestation of sarcoidosis, occurring in only 1-3% of patients.
Parenchymal changes from interstitial lung involvement may mimic airspace disease. The plain radiographic appearance of parenchymal disease may acquire a variety of radiographic patterns including fine nodular; reticulonodular; acinar (poorly marginated, small to large nodules or coalescent opacities); and, rarely, focal (solitary nodule or mass). In sarcoidosis, acinar opacities or interstitial granulomas may coalesce to give the appearance of alveolar form of sarcoidosis, which may exhibit an air bronchogram.
- Benign Lung Tumors
Benign lung tumors are a heterogenous group of neoplastic lesions originating from pulmonary structures. These tumors include bronchial adenomas, hamartomas, and a group of uncommon neoplasms (eg, chondromas, fibromas, lipomas, leiomyomas, hemangiomas, teratomas, pseudolymphomas, endometriosis).
Hamartomas (chondroadenomas) are the most common type of benign lung tumor. They mainly occur in adults but, on occasion, occur in children. Hamartomas are peripherally located. Grossly, they have a firm marblelike consistency. Histologically, hamartomas generally consist of epithelial tissue and other tissues such as fat and cartilage. Hamartomas can be easily enucleated, but wedge resection is also appropriate.
Bronchial adenomas make up 50% of all benign pulmonary tumors. The term bronchial adenoma, when used loosely, includes carcinoid tumors, adenocystic carcinomas, and mucoepidermoid carcinomas, which in fact are low-grade malignant tumors. The use of the term bronchial adenoma should be discouraged because it encompasses several benign and malignant tumors.
Mucous gland adenomas
Mucous gland adenomas are true benign bronchial adenomas. Mucous gland adenomas are also called bronchial cystadenomas, and they arise in the main or local bronchi. Histologically, they consist of columnar cell–lined cystic spaces with a papillary appearance.
Other rare tumor types
Multiple laryngeal papillomatosis is a viral disease of the upper airway that affects children. Multiple laryngeal papillomatosis has malignant potential and may spread to the tracheobronchial tree later.
Solitary papillomas usually are less than 1.5 cm in diameter. They usually are lobar or segmental in location and are histologically similar to viral papillomatosis.
Inflammatory papilloma is a solitary polypoid mass of granulation tissue that is associated with an underlying pulmonary inflammatory condition.
Granular cell myoblastomas are of neural cell origin. A granular cell myoblastoma contains polygonal or spindle cells with granular cytoplasm. Granular cell myoblastomas tend to be multiple in 10% of cases and are more common in men aged 30-50 years.
Other parenchymal tumors occasionally occurring in the endobronchial tree (eg, leiomyoma, lipoma) almost exclusively are found at an endobronchial location.
Solitary parenchymal tumors
Sclerosing hemangioma is an uncommon tumor derived from the epithelial cells of pneumocytes (terminal bronchiolar cells). This tumor consists of several elements, including solid cellular areas, papillary structures, sclerotic regions, and blood-filled spaces. This tumor is most commonly found in middle-aged women. Chest radiograph shows a well-defined nodule that is less than 4 cm.
Other mesenchymal tumors include lipoma, leiomyoma, neural tumors, fibroma, benign clear-cell tumor, teratoma, plasma cell granuloma, fibrous histiocytoma, xanthoma, pulmonary hyaline granuloma, pulmonary endometrioma, and pseudolymphoma.
Multiple parenchymal tumors
Many of these benign lung tumors may occasionally have multiple origins. Among these are hamartomas, hyalinizing granulomas, leiomyomas, and sclerosing hemangiomas.
The Carney triad is a syndrome of gastric epithelioid leiomyosarcoma, pulmonary chondromas, and extra-adrenal paragangliomas. The Carney triad mainly affects women.
Pulmonary tumorlets are minute collections of neuroendocrine cells scattered throughout the lung. Pulmonary tumorlets predominantly affect older women.
Clinically significant intrapulmonary chemodectomas apparently are paragangliomas. They behave in a benign fashion. Multiple minute pulmonary tumors, on the other hand, are of no clinical significance.
- Other Problems to be Considered:
Bronchogenic carcinoma – Small cell, large cell, adenocarcinoma, and squamous
Other infections – Aspergilloma, ascaris, dirofilariasis, echinococcal cyst, and bacterial abscess
Noninfectious granulomas – Rheumatoid arthritis, Wegener granulomatosis, and sarcoidosis
Developmental lesions – Bronchogenic cyst
Others conditions – Hematoma, bronchiolitis obliterans-organizing pneumonia, pseudotumor, pulmonary infarction, amyloidoma, rounded atelectasis, and mucoid impaction