Solitary Pulmonary Nodules
Solitary pulmonary nodules (SPNs) are very common. A
radiologist in an active practice may see one or more per day. Many
more are not perceived. At chest radiography, an SPN is seldom evident
until it is at least 9 mm in diameter (4
), and nearly 90% of newly discovered SPNs on chest radiographs may be visible in retrospect on prior radiographs (5
The importance of an SPN derives from the frequency with which it
represents a primary bronchogenic cancer. The causes of an SPN are many
), but more than 95% fall into one of three groups: (i) malignant neoplasms
, either primary or metastatic; (ii) infectious granulomas
, either tuberculous or fungal (Fig. 7-1
); and (iii) benign tumors, notably hamartoma
). In addition to specific radiologic features, clinical history is important in considering the likely cause of an SPN (Fig. 7-2
Bronchogenic carcinoma is rare in patients under 30 years of age and is
more common in cigarette smokers than nonsmokers. History of a
primary tumor makes a metastasis more likely than a new (or second)
primary tumor. Certain regions of the country are endemic for fungal
disease and therefore have a higher prevalence of benign nodules than
TABLE 7-1 CAUSES OF SOLITARY PULMONARY NODULES
Benign connective tissue and neural tumors (e.g., lipoma, fibroma, neurofibroma)
Inflammatory pseudotumor (plasma cell granuloma)
Bronchial atresia with mucoid impaction
Intrapulmonary lymph node
Normal confluence of pulmonary veins
Mimics of SPN
Cutaneous lesion (e.g., wart, mole)
Rib fracture or other bone lesion
"Vanishing pseudotumor" of congestive heart failure (loculated pleural effusion)
|SPN, solitary pulmonary nodule.
FIGURE 7-1. Granuloma. A: PA chest radiograph shows a small, well-circumscribed, round opacity at the right lung base (arrows). B:
Lateral view shows that the opacity is within the lung on two views
(posterior segment of the right lower lobe) and thus represents a
pulmonary nodule (arrow). The high density
of the nodule relative to its small size indicates that it is densely
calcified. The appearance is characteristic of a benign calcified
granuloma, and no further evaluation of the nodule is needed (an
exception would be in a patient with a known calcium-producing primary
tumor, such as osteosarcoma, which can lead to calcified pulmonary
metastases; in this case, older radiographs confirmed over 2 years of
stability of the granuloma).
Management options with an SPN include further imaging
workup, declaration of benign etiology and no further evaluation,
follow-up (usually with CT), or tissue diagnosis (either with
percutaneous or transbronchial biopsy or via surgical resection).
Management algorithms should take into account radiologic and clinical
factors. Such additional information may obviate further workup (Fig. 7-3).
Two rules must be remembered when evaluating an SPN:
first, a "nodule" is not confirmed to be within the lung unless it is
seen in the lung on both posteroanterior (PA) and lateral chest
radiographs or it is seen in the lung on a chest CT. Second, the
current radiograph or CT scan should be compared with prior radiologic
studies, when available, to confirm the chronicity of the nodule.
Following these two basic rules will, on occasion, prevent unnecessary
further workup and concern.
FIGURE 7-2. Postbiopsy hematoma.
This 62-year-old man underwent transbronchial biopsy of the right
middle lobe 11 days after lung transplantation. The history supports
hematoma as the cause of the nodule in the right lung. A: CT scan shows a ground-glass nodule with central cavitation (arrow) in the right middle lobe. B: At a more inferior level, the nodule (arrow) appears more solid.
Four important considerations in the evaluation of an
SPN are (i) attenuation characteristics, (ii) rate of growth, (iii)
shape, and (iv) size. Each of these will be discussed separately;
however, it should be noted that no single radiologic feature or
combination of features is entirely specific for lung carcinoma or
other primary malignant tumors.
The presence or absence of calcium is the most important
feature that distinguishes benign from malignant nodules.
Unfortunately, 45% of benign nodules are not calcified (6
Benignity can be confirmed confidently if the lesion is smaller than 3
cm in diameter, is smoothly marginated, and exhibits one
the following patterns of calcification: large central nidus,
laminated, popcorn, or diffuse. All other patterns of calcification are
less specific, as further described later. SPNs smaller than 9 mm in
diameter are rarely visible on chest radiographs, and a nodule of this
size that is clearly seen is likely to be diffusely calcified and
benign (Fig. 7-1
Dual-energy subtraction chest radiography can better depict
calcification in pulmonary nodules compared with conventional chest
). So-called popcorn
calcifications, which are randomly distributed, often overlapping rings
of calcium, are seen when cartilage is present, such as with a
hamartoma (Fig. 7-4
). Large areas of dystrophic
calcium are essentially diagnostic of benign nodules, usually
granulomas, and the exceptions are extremely rare. Any calcium in a
nodule makes the nodule more likely to be benign. When calcium is
detected on thin-section CT (=3-mm sections), even when not diffuse and
not obviously benign in nature, the likelihood of benignity is high
enough to warrant follow-up imaging. This management is recommended,
however, only for nodules that are otherwise smoothly marginated, 3 cm
or smaller in diameter, and not increasing in size at a rate compatible
with bronchogenic carcinoma (Fig. 7-5
The presence of eccentric calcium in a nodule occasionally represents a
sign of "scar carcinoma," where the cancer has arisen from a granuloma
or engulfed a fibrotic, calcified granuloma. Central calcification in a
spiculated SPN should be viewed with suspicion, because most benign
SPNs have smooth or minimally lobulated margins. Calcifications in lung
cancers may appear amorphous, stippled, or diffuse, and some can have
dense foci of calcification or be entirely calcified, with a pattern
resembling that of benign disease. These last two patterns
be seen in carcinoid tumors, metastatic osteosarcoma, and
chondrosarcomas. Stippled calcification can be seen in metastases from
mucin-secreting tumors such as colon or ovarian cancers.
FIGURE 7-3. Dependent atelectasis. A: Supine CT image shows a small rounded opacity (arrow) in the dependent right lower lobe. B: The "nodule" disappears on prone imaging, confirming the etiology to be focal atelectasis.
FIGURE 7-4. Hamartoma. A: PA chest radiograph shows a rounded opacity in the left middle lung with calcification (arrows). B:
PA chest radiograph obtained 5.5 years later shows enlargement of the
nodule, which has doubled in volume. The randomly distributed
calcifications, arranged in overlapping rings, now have the typical
"popcorn" appearance described with hamartomas. It is not unusual for
hamartomas to enlarge; unlike malignant nodules, however, the growth
rate is slow, with doubling occurring in more than 18 months' time.
FIGURE 7-5. Small-cell carcinoma. A:
CT image shows an irregular, calcified, round nodule in the right lower
lobe. The pattern of calcification is not definitely benign and the
nodule's irregular margin makes it suspicious for neoplasm. B: CT scan with lung windowing shows the nodule to have a lobulated contour.
If fat is present within a nodule, the most likely
diagnosis is hamartoma, and less likely diagnoses are lipoma or
myelolipoma. Exceptions include metastatic liposarcoma or renal cell
carcinoma, which rarely present as fat-containing nodules on CT.
are benign lesions
consisting of an abnormal mixture of the normal constituents of the
lung. Most pulmonary hamartomas contain masses of cartilage and may
also contain fat or cystic collections of fluid (Figs. 7-6
). They grow slowly and are usually solitary (see Fig. 7-4
). More than 90% are peripheral in location
Pulmonary hamartomas can range up to 10 cm in diameter, although most
are less than 4 cm, and are usually spherical, lobulated, or notched
with a very well-defined edge. In patients without prior malignancy,
focal fat attenuation (-40 to -120 Hounsfield units) is a reliable
indicator of a hamartoma (10
FIGURE 7-6. Hamartoma. A:
PA chest radiograph shows an approximately 2-cm round nodule
superimposed over the left first rib end that is partially obscured by
an external electrocardiogram lead (arrows).
This nodule was not recognized at the time the radiograph was taken
because it was "hiding" among the shadows of overlapping bones in the
upper lung. B: PA chest radiograph obtained 3 years later shows that the nodule has not changed (arrows). This period of stability is consistent with benign etiology. C: CT scan shows calcification (arrow) and fat (arrowhead) within the nodule, characteristic of a benign hamartoma.
FIGURE 7-7. Hamartoma. A: CT scan shows a round, circumscribed nodule with coarse central calcification in the periphery of the right lower lobe (arrow). B: CT scan at a more inferior level shows central low attenuation (-40 Hounsfield units) (arrow) consistent with fat.
On CT, nodules can be described as solid, partly solid,
or nonsolid. Aerated lung is visible through a nonsolid (ground-glass)
nodule. Whereas most cancerous nodules are solid, partly solid nodules
are most likely to be malignant and are often caused by
bronchioloalveolar cell carcinoma (Figs. 7-8, 7-9, 7-10). Air bronchograms and bronchiolograms are seen more commonly in pulmonary carcinomas than in benign nodules.
An SPN that exhibits no growth for at least 2 years is generally considered benign (11).
However, even benign lesions, such as granulomas, can grow slowly.
Therefore, growth alone cannot be used to predict malignancy.
Bronchogenic carcinomas usually take between 1 and 18 months to double
in volume (12). A volume doubling is a change
in diameter of about 1.25 times the previous diameter. Doubling times
that are faster than 1 month suggest infection, infarction, histiocytic
lymphoma, or a fast-growing metastasis from tumors such as germ cell
tumor, lymphoma, melanoma, and soft tissue sarcoma (Table 7-2) (13).
Doubling times slower than 18 months suggest granuloma, hamartoma,
bronchial carcinoid, salivary gland adenoid cystic carcinoma, thyroid
carcinoma metastases, and round atelectasis. However, there are
exceptions, and cancerous tumors with doubling times of more than 730
days may appear stable during a 2-year observation period. Growth is
more accurately assessed on CT than on chest radiography, and diameters
measured with electronic calipers are preferable to diameters measured
manually. However, many factors, including size of the nodule and
determination of the nodule margin, can limit the accuracy of
measurement. It is difficult to reliably show changes in size that are
smaller than 2 mm, and even a substantial increase in volume may be
missed with small nodules.
FIGURE 7-8. Bronchioloalveolar cell carcinoma. CT scan shows a mixed solid/ground-glass nodule in the periphery of the left lower lobe (arrows). Internal "bubble" lucencies are a characteristic feature of this type of neoplasm.
Edge characteristics indicative of malignancy include irregularity, spiculation, and lobulation (Fig. 7-11
). A corona radiata
described as numerous strands radiating from the nodule into the
surrounding lung, is very suggestive of bronchogenic carcinoma,
although there are exceptions in which a corona radiata is seen in
benign lesions such as infectious granulomas and other chronic
inflammatory lesions (15
). The "tail sign"
consists of a linear opacity that extends from a peripheral nodule to
the visceral pleura; for some years this sign was regarded as a
reliable sign of malignancy. Studies have shown, however,
that up to half of nodules showing the tail sign represent benign granulomas (16
and therefore the tail sign is a nonspecific feature of peripherally
located pulmonary lesions that cannot be used to distinguish a benign
from a malignant lesion. Lobulation and notching are seen with both
benign and malignant nodules and are not very useful discriminating
features (Figs. 7-12
A well-defined, smooth, nonlobulated edge is most compatible with
hamartoma, granuloma, or metastasis. However, a smooth margin does not
indicate benignity, as up to one third of malignant lesions have smooth
). Therefore, the previously mentioned signs are more helpful in their absence. Adjacent tiny nodules, called satellite nodules
, are strongly associated with benignity (Fig. 7-12
) but do not allow a confident diagnosis of benignity, as 10% of dominant nodules with satellite nodules will be malignant (Fig. 7-15
FIGURE 7-9. Bronchioloalveolar cell carcinoma. CT scan shows a mixed solid and ground-glass nodule in the left upper lobe (arrow).
FIGURE 7-10. Bronchioloalveolar cell carcinoma. CT scan shows a poorly defined ground-glass nodule in the right upper lobe (arrow).
FIGURE 7-11. Primary adenocarcinoma. A:
Preoperative chest radiograph of an asymptomatic 68-year-old woman with
an abdominal aortic aneurysm shows a subtle, small nodule (arrow) in the left upper lobe. B: The nodule (arrow) is more apparent on dual-energy chest radiography, optimized for lung evaluation. C: CT scan shows that the nodule has irregular margins (arrow).
TABLE 7-2 FAST-GROWING PULMONARY METASTASES
|"Loves to Multiply Swiftly"
Testicular germ cell tumor
Soft tissue sarcoma (osteosarcoma)
FIGURE 7-12. Coccidioidomycosis. A:
PA chest radiograph of a 38-year-old woman living in California with a
remote history of pneumonia shows a slightly lobulated, 3-cm nodule in
the superior segment of the left lower lobe (arrows), which had enlarged compared with chest radiograph from 3 months earlier (not shown). B: CT scan shows a dominant nodule, slightly lobulated and notched, and adjacent smaller satellite nodules (arrows).
Satellite nodules are more commonly seen with benign entities, but they
can be seen with malignant neoplasms and therefore cannot be used to
distinguish benign from malignant nodules. Coccidioidomycosis occurs in
the southwest United States and was the suspected diagnosis.
FIGURE 7-13. Large-cell bronchogenic carcinoma. A:
PA chest radiograph of a 45-year-old cigarette smoker with a cough for
3 months shows an approximately 3-cm nodule in the left upper lobe (arrows),
which was new compared to prior chest radiographs. Note the similarity
between the appearance of this nodule and the nodule in Figure 7-12. B: Lateral view confirms the location of the nodule in the anterior left upper lobe (arrows), with no visible calcification. C: CT scan shows that the nodule is slightly lobulated but fairly well circumscribed. The tail sign is present (arrow);
this is a nonspecific feature of peripherally located pulmonary lesions
that does not distinguish a benign from a malignant lesion.
FIGURE 7-14. Non–small-cell bronchogenic carcinoma. A: Chest radiograph shows a subtle nodular opacity adjacent to the left heart border (arrow). B: CT scan shows a slightly lobulated nodule with smooth margins in the left lower lobe (arrow).
SPNs with irregular-walled cavities thicker than 16 mm
tend to be malignant, whereas benign cavitated lesions usually have
thinner, smoother walls. However, because there is considerable
overlap, cavity wall characteristics cannot be used to confidently
differentiate benign and malignant SPNs (Figs. 7-16 and 7-17) (18).
Sequential thin-section CT (1- to 3-mm section width)
performed through an entire nodule with a single breath hold provides
information regarding nodule size, attenuation, edge characteristics,
and the presence of calcification, cavitation, or fat. In some cases,
the findings will provide evidence that the nodule is benign. However,
the cause of many SPNs will remain undetermined. If the nodule is at
least 10 mm in diameter, a contrast–enhanced CT may be performed. The
nodule is examined with 3-mm collimation before and after
administration of intravenous contrast material. Contrast-enhanced
images are acquired at 1-minute intervals up to 4 minutes after
injection of contrast material. Nodule enhancement of less than 15
Hounsfield units after administration of contrast material is strongly
indicative of benignity. Although enhancement
more than 15 Hounsfield units is more likely to represent malignancy,
the false-positive rate is high and is caused by active inflammatory
disease such as granulomas or organizing pneumonias. Therefore, nodule
enhancement is a sensitive but nonspecific indicator of malignancy (19
FIGURE 7-15. Primary squamous cell carcinoma. CT scan shows a dominant nodule (arrow) with adjacent smaller irregular nodules and ground-glass opacities.
FIGURE 7-16. Invasive pulmonary aspergillosis. CT scan of a 52-year-old woman with a liver transplant shows a thick-walled, irregular, cavitary mass in the right lower lobe.
FIGURE 7-17. Primary adenocarcinoma. CT scan of a 66-year-old woman with idiopathic pulmonary fibrosis shows a cavitary spiculated nodule in the left upper lobe (arrow).
Positron emission tomography (PET) with
fluorine-18-fluorodeoxyglucose of SPNs larger than 1 cm in diameter is
being used with increased frequency to determine whether a lesion is
malignant or benign (20). For SPNs 1 to 3 cm in diameter, sensitivity and specificity are approximately 94% and 83%, respectively (21).
False-positive PET findings are associated with focal infections,
inflammation, and granulomatous diseases such as tuberculosis and
sarcoidosis. False-negative PET findings are seen with carcinoid and
bronchioloalveolar cell carcinoma, tumors that have a low metabolic
rate. Sensitivity and specificity of PET decreases with nodules smaller
than 1 cm in diameter.
FIGURE 7-18. Benign lymph node. A: Chest radiograph shows a subtle nodule (arrow) in the left lower lobe. B: CT scan (5-mm slice thickness) shows that the nodule has smooth margins (arrow). C: Thin-section CT scan (1.25 mm thickness) shows that the nodule (arrow)
is along the left major fissure, consistent with a benign subpleural
lymph node. Although the CT findings were highly suggestive of the
diagnosis, fine-needle aspiration biopsy was performed and the
diagnosis was confirmed.
Radiologists are frequently asked to perform
percutaneous fine-needle aspiration biopsy (FNAB) of pulmonary nodules.
CT allows for biopsy of many nodules as small as 5 mm in diameter. In
patients who are not candidates for surgery, FNAB can be performed to
confirm and determine the histologic type of malignancy. In patients
who are candidates for surgery, FNAB can confirm benign disease.
Contraindications to FNAB include inability of the patient to hold the
breath, lie immobile on the CT table for more than 30 minutes, or
refrain from coughing. Relative contraindications include bleeding
diatheses, previous pneumonectomy, severe emphysema, severe hypoxemia,
pulmonary artery hypertension, or nodules in which successful biopsy
cannot be performed because of their small size or location. FNAB has a
sensitivity of 86% and a specificity of 98.8% in the diagnosis of
). Sensitivity decreases for
nodules 5 to 7 mm in diameter and in patients with lymphoma. When the
FNAB sample is interpreted as malignant or if a specific benign
condition is diagnosed (Fig. 7-18
), further decisions regarding care are dictated by the
diagnosis. When a nonspecific benign condition is diagnosed, such as
atypical bronchioloalveolar hyperplasia or inflammation without
organisms on a smear or a culture, further evaluation with core-needle
biopsy or clinical and radiologic follow-up is required. The most
common complications of FNAB are pneumothorax and hemorrhage, with
pneumothorax occurring in 25% of patients.
7-3 SUGGESTED RECOMMENDATIONS FOR FOLLOW-UP AND MANAGEMENT OF NODULES
DETECTED INCIDENTALLY ON CT IN PATIENTS 35 YEARS OF AGE OR OLDER
WITHOUT KNOWN CANCER
|Size of nodule
|5 to 6 mm
|7 to 8 mm
||3/9/24/stop or PET or Bx
||3/9/24/stop or PET or Bx
computed tomography; F/U, follow-up, with intervals shown in months;
"stop" refers to no additional F/U in nodules that have shown no change
in the interval recommended; Bx, biopsy; PET, positron emission
tomography; mm refers to average of nodule length and width.
The ability to detect very small nodules improves with
each new generation of CT scanner. The majority of cigarette smokers
who undergo thin-section CT have been found to have small lung nodules,
most of which are smaller than 7 mm in diameter (23).
Guidelines for follow-up and management of noncalcified nodules
detected on nonscreening CT scans were developed before widespread use
of multidetector row CT and still indicate that every indeterminate
nodule should be followed with serial CT for a minimum of 2 years.
Recently, the Fleischner Society published guidelines for management of
SPNs that are detected incidentally on CT scans (24).
The Fleischner Society recommendations apply only to adult patients (35
years of age or older) with nodules that are “incidental in the sense
that they are unrelated to known underlying disease.” In patients under
age 35, unless they have a known primary cancer, the guidelines suggest
that a single low-dose follow-up CT in 6 to 12 months be considered.
Patients with a cancer that may be a cause of lung metastases should be
cared for according to the relevant protocol or specific clinical
situation. Longer follow-up intervals are recommended for nonsolid
(ground-glass) and very small opacities. An abbreviated set of
recommendations for nodule follow-up, based on the Fleischner
guidelines, is shown in Table 7-3.
Multiple Pulmonary Nodules
The differential diagnosis for multiple pulmonary nodules is different from that for SPNs (Table 7-4),
although there is some overlap. In more than 95% of patients with
multiple pulmonary nodules, the etiology of the nodules is (a)
metastases or (b) tuberculous or fungal granulomas (Fig. 7-19) (2). Determining that the nodules are cavitary is useful in narrowing the list of diagnostic possibilities (Figs. 7-20, 7-21, 7-22; Table 7-5) (25).
A cavity is defined as a gas-filled space within a zone of pulmonary
consolidation or within a mass or nodule that is produced by the
expulsion of a necrotic part of the lesion via the bronchial tree; the
lucent portion is surrounded by a wall of varied thickness, and there
may or may not be an accompanying fluid level (1).
Those disorders that can result in cavitary nodules can also result in
nodules that are not cavitary or that are not appreciated as cavitary
on a chest radiograph; therefore, the mnemonic for cavitary nodules,
"CAVITY" (Table 7-5), can be remembered as a guide for all cases of multiple pulmonary nodules.
The great majority of patients who have multiple noncalcified nodules on chest radiographs have metastases.
This is even more likely to be the diagnosis when the patient has a
known or suspected primary malignancy. The larger and more variable in
size that the nodules are, the more likely they are to be neoplastic.
Metastases are usually spherical with well-defined margins; as a rule,
they vary considerably in size. In autopsy series, the most common
sources of metastases from extrathoracic malignancies to the lungs
include tumors of the breast, colon (Figs. 7-23
), kidney, uterus, prostate, head, and neck (26
Other tumors that have a high incidence of pulmonary metastases, but
are not as prevalent in the population and therefore not encountered as
frequently, include choriocarcinoma, osteosarcoma, Ewing sarcoma,
testicular tumors (Figs. 7-25
), melanoma, and thyroid carcinoma. The most common sites of origin of cavitary metastases are the uterine cervix (Fig. 7-27
), colon, and head and neck (Fig. 7-28
). Squamous cell carcinoma cavitates twice as often as adenocarcinoma (27
). Calcification of metastases is seen most commonly with osteosarcoma and chondrosarcoma (Fig. 7-29
) or after successful treatment of metastases (28
A miliary nodular pattern of metastases is seen most commonly with
thyroid or renal carcinoma, bone sarcoma, trophoblastic disease,
melanoma. On occasion, an SPN will be seen in a patient with a known
primary tumor. In a patient over age 35 with a squamous cell cancer
elsewhere in the body, the solitary lung lesion is usually a separate
primary tumor. If the patient has adenocarcinoma elsewhere, there is an
equal chance that the solitary nodule is a primary lung cancer or a
solitary metastasis. Cancer of the colon is the most common source of a
solitary pulmonary metastasis. If there is a soft tissue or skeletal
sarcoma or a melanoma elsewhere, the solitary lung lesion is most often
a metastasis (29
TABLE 7-4 CAUSES OF MULTIPLE PULMONARY NODULES
Malignant lymphoma/lymphoproliferative disorders
Fungal and opportunistic infections
Langerhan cell histiocytosis
Arteriovenous malformations (Osler-Weber-Rendu Syndrome)
FIGURE 7-19. Acute histoplasmosis. A: PA chest radiograph of a 41-year-old man with cough and fever shows multiple ill-defined nodular opacities bilaterally. B:
PA chest radiograph obtained 9 years later shows numerous bilateral
small calcified granulomas, the residua of prior fungal infection. The
nodules are all less than 1 cm in diameter but are seen very well
because they are densely calcified.
FIGURE 7-20. Wegener granulomatosis. A: PA chest radiograph shows a large cavitary mass in the left lung, demonstrating an air–fluid level (arrows). B: CT image shows the large left cavitary mass and numerous smaller cavitary nodules (arrows).
FIGURE 7-21. Blastomycosis. A: PA chest radiograph shows focal airspace opacity in the left lung and a small nodule in the right mid lung. B: CT scan shows a cavitary nodule in the right upper lobe (arrow), several other irregular nodules, and dense airspace disease in the left upper lobe.
FIGURE 7-22. Coccidioidomycosis. A:
PA chest radiograph of a 40-year-old man with cough and fever shows a
3-cm cavitary nodule in the superior segment of the left lower lobe (arrows). B: CT image shows a soft tissue mass within the cavity (arrows),
characteristic of a "fungus ball." On occasion, bronchogenic cancer
(especially one of squamous cell histology) can cavitate, and bleeding
can result in an intracavitary hematoma, with an appearance similar to
that of a fungus ball. A fungus ball will usually roll around inside
the cavity with changes in patient positioning.
The most common sources of septic emboli
are infected venous catheters (including pacemaker wires) (Fig. 7-30
valvular endocarditis, septic thrombophlebitis, and indwelling
prosthetic devices. Septic embolism is a well-known complication of
intravenous drug abuse. The diagnosis of septic emboli is usually
established by positive blood cultures, although the radiologic
findings, especially those on CT of the chest, may be visible before
blood cultures become positive (30
). The usual
radiographic and CT appearance consists of multiple peripheral
pulmonary opacities that occur in any portion of the lungs but more
prevalent in the lower lungs because of the greater pulmonary blood
flow to this region. The lesions are usually either round or wedge
shaped, as with a pulmonary infarct. Approximately 50% of the lesions
). The presence of a distinct vessel leading to the apex of a peripheral area
of consolidation, seen in bland and infected infarcts, has been termed the feeding vessel sign
This sign is not specific for but is more commonly seen with pulmonary
emboli than in other conditions. The combination of multiple peripheral
nodules or wedge-shaped consolidations, some of which are cavitated,
and a distinct feeding vessel in the appropriate clinical setting is
highly suggestive of the diagnosis of septic emboli (Fig. 7-31
TABLE 7-5 CAUSES OF CAVITARY PULMONARY NODULES
Carcinoma (bronchogenic, metastases - especially squamous cell)
Autoimmune (Wegener granulomatosis, rheumatoid nodules)
Vascular (bland and septic emboli)
Infection (especially mycobacterial and fungal)
Young - i.e., congenital (sequestration, diaphragmatic hernia, bronchogenic cyst)
|Reproduced with permission from Dähnert W. Radiology Review Manual. Baltimore: Williams & Wilkins; 1991.
FIGURE 7-23. Colon cancer metastases.
PA chest radiograph shows multiple bilateral pulmonary nodules of
varying sizes. The nodules do not appear well circumscribed, but their
appearance does not exclude the likely diagnosis of metastases in a
patient with known colon cancer, a tumor that is a common source of
metastases to the lungs.
FIGURE 7-24. Colon cancer metastases. A: PA chest radiograph shows small bilateral pulmonary nodules. B: CT scan shows numerous small circumscribed pulmonary nodules (arrows). The nodule margins are better defined on CT compared with chest radiography.
FIGURE 7-25. Metastatic testicular carcinoma. PA (A) and lateral (B)
chest radiographs show numerous bilateral well-circumscribed pulmonary
nodules of varying sizes, typical of pulmonary metastases. Testicular
carcinoma has a high incidence of pulmonary metastases. Note on the PA
view that some of the nodules are "hiding" under the diaphragm (arrows)
in the posterior lung bases. It is important to always look carefully
in this area for nodules, as they are more difficult to see when they
are not contrasted with the lucency of the air-filled anterior lung.
Pulmonary arteriovenous malformations
(AVMs) are fistulous vascular communications between a pulmonary artery and vein (95%) (Fig. 7-32
or a systemic artery and pulmonary vein (5%) that can be single or
multiple. When multiple, nearly 90% of cases are associated with
Osler-Weber-Rendu disease (hereditary hemorrhagic telangiectasis), a
syndrome of epistaxis, telangiectasia of skin and mucous membranes, and
gastrointestinal bleeding. AVMs are usually a congenital defect of
structure, but they can be acquired in cirrhosis, cancer, trauma,
surgery, or certain infections. The typical radiographic appearance of
an AVM is a sharply defined, lobulated oval/round mass, from less than
1 cm to several centimeters in size, associated with an enlarged
feeding artery and draining vein. On CT, AVMs will typically
demonstrate marked contrast enhancement (Fig. 7-33
Shunting from the fistula can result in hypoxia, systemic abscesses, or
infarction, notably of the brain, because the right-to-left shunting of
blood bypasses the filtering capacity of the lung (32
). Multiple AVMs can be confused with metastases if the enlarged feeding vessels are overlooked.
FIGURE 7-26. Metastatic melanoma. A:
PA chest radiograph shows multiple bilateral well-circumscribed
pulmonary nodules and masses of varying size. The appearance has given
rise to the term "cannonball" metastases. B: Lateral view confirms the presence of the nodules and masses in the lungs.
FIGURE 7-27. Cervical carcinoma metastases. A:
PA chest radiograph shows multiple bilateral pulmonary nodules, some of
which are fairly well circumscribed. The periphery of the lungs “fades
out” because of the patient's large body habitus and abundant soft
tissues of the chest wall. B: CT image shows that many of the nodules are cavitary (arrows),
and all are well circumscribed. The uterine cervix is one of the most
common sites of origin of cavitary pulmonary metastases.
FIGURE 7-28. Tonsillar squamous cell carcinoma metastases. A: PA chest radiograph of a 50-year-old man with a 20–pack-year history of cigarette smoking shows multiple bilateral cavitary (solid arrow) and noncavitary (dashed arrow) nodules. B: CT scan shows that the cavitary nodules have thin walls.
FIGURE 7-29. Metastatic osteosarcoma. A:
PA chest radiograph of a 57-year-old man with cough and hemoptysis and
a history of mandibular resection for chondroblastic osteosarcoma 7
years prior shows a large lobulated right hilar mass (arrows). B: Lateral view confirms the hilar location (arrows). C: CT scan shows coarse areas of calcification within the mass. D: CT at a level inferior to (C) shows that the tumor extends into the left atrium (arrows). E: CT with lung windowing shows a small pulmonary metastasis in the right upper lobe (small arrow) and a larger, densely calcified metastasis in the left upper lobe (large arrow). F:
Magnetic resonance (MR) imaging (repetition time 631, echo time 10,
spin echo, 5-mm thickness), coronal view, shows that the tumor (large arrows) is growing through the right superior pulmonary vein into the left atrium (small arrows). G: MR (repetition time 66, echo time 13, SPGR [AU: What is meant by SPGR? Spoiled gradient recall? Please spell out.], 7-mm thickness) axial view, shows low-signal tumor (large arrows) invading the normal high-signal-intensity left atrium (LA). Note high signal within left inferior pulmonary vein (small arrows).
FIGURE 7-30. Septic emboli.
CT scan of a 51-year-old woman on hemodialysis for end-stage renal
disease and elevated white blood cell count shows nodules, one of which
is cavitary (arrow), in the right upper lobe. The patient's hemodialysis catheter was the source of the septic emboli.
FIGURE 7-31. Septic emboli. A: PA chest radiograph shows numerous cavitary (solid arrow) and noncavitary (dashed arrow) nodules and masses in the lung and bilateral pleural effusions. B: CT image shows multiple nodules, some cavitary, in the periphery of the lungs, a common location for septic emboli to appear. C: CT at a level inferior to (B) shows multiple nodules in the right lung, the feeding vessel sign (arrow), and a dominant cavitary mass in the left lung.
FIGURE 7-32. Arteriovenous malformation. CT scan of a 36-year-old woman with hemoptysis shows a tubular structure in the right lower lobe (arrow), representing a large feeding artery and draining vein.
FIGURE 7-33. Arteriovenous malformation. A: CT image of a 62-year-old woman with Rendu-Osler-Weber syndrome shows a tubular structure in the inferior right middle lobe (arrow). B: CT with soft tissue windowing shows that the structure enhances densely with intravenous contrast (arrow).
Pneumatoceles are cystic air collections within the lung that result from infection (most notably Streptococcus pneumoniae, Escherichia coli, Klebsiella, and Staphylococcus);
blunt or penetrating trauma to the chest; or hydrocarbon inhalation (as
from furniture polish or kerosene). In the case of trauma, the
pneumatocele represents a laceration that evolves from a lung opacity
to a thin-walled cystic structure to a linear scar. Depending on the
stage of evolution, a pneumatocele may resemble a cavitary mass, and
when multiple they may resemble and be misdiagnosed as metastases or
multifocal lung abscesses if the clinical history is not taken into
Congenital lesions, including sequestration,
diaphragmatic hernia, and bronchogenic cyst, can appear as cavitary
nodules or masses on chest radiography and are therefore included in
the differential diagnosis of cavitary nodules. These entities are
discussed further in Chapters 6 and 16.