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1 Department of Radiology, New York University Medical Center, New York, NY
10016.
2 Department of Radiology, Mayo Clinic College of Medicine, Scottsdale, AZ
85259.
3 Department of Radiology, University of Arizona, Tucson, AZ 85724.
4 Department of Radiology, University of Washington, Box 354755, 4245 Roosevelt
Way NE, Seattle, WA 98105.
Received October 2, 2006;
revised November 22, 2006;
Address correspondence to F. S. Chew
(fchew{at}u.washington.edu).
Abstract
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Keywords: lung • solitary pulmonary nodule
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1
cm) detected at population-based CT screening for lung cancer: reliable
high-resolution CT features of benign lesions. AJR 2003;
180:955-964 |
TopAbstractINTRODUCTIONEDUCATIONAL OBJECTIVESREQUIRED READINGRECOMMENDED READINGINSTRUCTIONSReferences |
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TopAbstractINTRODUCTIONEDUCATIONAL OBJECTIVESREQUIRED READINGRECOMMENDED READINGINSTRUCTIONSReferences |
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| QUESTION 1 Which of the following is a solitary pulmonary nodule with poorly defined margins LEAST likely to be?
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| QUESTION 2 For a solitary pulmonary nodule, which imaging feature most favors a malignancy?
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| QUESTION 3 For a well-circumscribed solitary pulmonary nodule, which CT feature most favors necrosis due to granulomatous disease rather than malignancy?
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| QUESTION 4 For a solitary pulmonary nodule, which pattern of calcification is associated with malignancy?
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| QUESTION 5 Concerning the subsolid solitary pulmonary nodule, which option is FALSE?
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| QUESTION 6 Concerning 18F-FDG PET for lung nodule evaluation, which option is FALSE?
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| QUESTION 7 For solitary pulmonary nodules measuring < 1 cm, which CT feature is characteristically seen only in benign nodules?
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| QUESTION 8 For solitary pulmonary nodules measuring < 1 cm, which combination of CT features has the highest sensitivity and specificity for benign lesions?
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| QUESTION 9 Which statement is TRUE regarding the CT followup of indeterminant solitary pulmonary nodules?
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| QUESTION 10 Which of the following is TRUE regarding evaluation of a pulmonary nodule on chest radiographs?
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Solution to Question 1
Poorly defined margins refer to ground-glass opacity at the borders of a
nodule. Poorly defined margins have been identified in a number of entities
and may correlate with hemorrhage or early cellular infiltration
[1]. Thus, poorly defined
margins may occur with Wegener's granulomatosis, angioinvasive aspergillosis,
bronchioloalveolar carcinoma, and hemorrhagic metastases. Options A, B, C, and
D are not the best responses. Hamartomas have well-defined borders. Option
E is the best response.
Solution to Question 2
Several CT characteristics favor either a benign or a malignant cause for a
solitary pulmonary nodule. A solitary pulmonary nodule with irregular,
spiculated borders is suspicious for malignancy. Option D is the best
response. A round to oval solitary pulmonary nodule with smooth margins is
more characteristic of a benign process. Option B is not the best response.
For nodules larger than 7 mm, the study of contrast enhancement can be used to
identify those that are benign but not those that are malignant
[2]. A maximal increase in
attenuation of less than 15 H is indicative of a benign diagnosis, whereas an
increase of 15 H or more is nonspecific. Malignant lesions and granulomas with
active inflammatory changes may enhance substantially more than 15 H. Option A
is not the best response. A nodule with a low-density center and a smooth
enhancing rim—the "enhancing rim" sign—also favors a
benign process [3]. The
enhancing rim sign is seen in necrotizing granulomas. Option C is not the best
response. Chronic granulomas often have coarse central calcifications. Option
E is not the best response.
Solution to Question 3
Both benign and malignant solitary pulmonary nodules can have central
necrosis. The CT feature that suggests necrosis caused by a necrotizing
granuloma is homogeneous low density of the necrotic region
[3]. Option A is the best
response. Necrotic centers in malignant masses are heterogeneous in
density. Malignant masses also tend to be larger than 3 cm before they show
signs of necrosis. The absolute density of the necrotic region, the percentage
of the mass involved, and the presence of ground-glass opacification have not
been proven to be differentiating features. Options B, C, and E are not the
best response. Intense enhancement of a necrotic region would not be expected
in either benign or malignant masses. Option D is not the best response.
Solution to Question 4
The presence of calcification in a pulmonary nodule generally indicates a
benign cause. However, malignant pulmonary nodules may show calcification, and
consequently the pattern of calcification also must be taken into
consideration. Additionally, the ratio of soft tissue to calcification should
be considered, particularly for larger nodules, because lesions with a high
percentage of soft tissue or calcifications not distributed throughout the
nodule are generally considered indeterminate. A peripheral rim of
calcification is considered a subtype of laminar or target pattern
calcification and indicates a benign cause, typically a histoplasmoma. Option
A is not the best response. Multiple conglomerate foci, also called
"popcorn" calcification, are typical of a hamartoma. Option B is
not the best response. The presence of central calcification is usually
considered benign. However, some tumors (mucinous adenocarcinoma and
carcinoid) can show central calcification, and follow-up imaging should be
considered if a large soft-tissue component is present (i.e., the
calcification is small relative to nodule size), if the nodule is greater than
2 cm, if the nodule shows spiculated margins, and if the calcification is not
truly central. Option C is not the best response. Diffuse or complete
calcification is indicative of a benign cause. Option D is not the best
response. Eccentric calcification and small flecks of calcification (stippled
calcification) may be observed in malignant nodules [4]. Option E is the
best response.
Solution to Question 5
The subsolid nodule is a descriptor used to refer to nodules containing a
component of ground-glass attenuation [5]. Groundglass attenuation is defined
as an increase in lung attenuation that is not dense enough to obscure the
surrounding vessels. Subsolid nodules may be of pure ground-glass attenuation
(nonsolid) or of part ground-glass attenuation and part higher-density
components (part solid). The subsolid nodule has primarily been associated
with the spectrum of adenocarcinoma but may also occur in inflammation.
Atypical adenomatous hyperplasia is now considered a precursor of
adenocarcinoma and manifests as a pure grounds-glass nodule, typically less
than 1 cm. Options A, B, D, and E are not the best responses. Squamous cell
malignancy typically presents as a solid nodule or a mass that may contain
cavitation. The subsolid nodule is not associated with squamous cell
malignancy. Option C, which is false, is the best response.
Solution to Question 6
PET for diagnosing a nodule as malignant has a sensitivity and specificity
of 96% and 88%, respectively
[6]. False-positive findings
(high standardized uptake values) may occur with various granulomatous
conditions as well as with lipoid pneumonia. Option A is not the best
response. Low uptake on PET can result when a lesion is beyond the resolution
of PET scanners, regardless of whether the lesion is malignant or benign.
Bronchioloalveolar carcinoma and carcinoid tumors have been associated with
low uptake on 18F-FDG PET; therefore, low uptake does not always
correlate with a benign entity. Option B, which is false, is the best
response. Options C, D, and E are not the best responses.
Solution to Question 7
Of the listed high-resolution CT characteristics, polygonal shape is seen
only in benign lesions [7].
Option A is the best re- sponse. The other CT findings of
predominantly solid, peripheral subpleural location, coarse spiculation, and
air bronchograms are seen in both benign and malignant lesions. A peripheral
subpleural location is seen in 33% of benign lesions and 8% of malignant
lesions. Option B is not the best response. A predominantly solid
characteristic is seen in 93% of benign lesions and 20% of malignant lesions.
Option C is not the best response. Coarse spiculation is seen in 20% of benign
lesions and 12% of malignant lesions. Option D is not the best response. Air
bronchograms are seen in 13% of benign lesions and 32% of malignant lesions.
Option E is not the best response.
Solution to Question 8
The combination of CT features that is most sensitive and specific for
benign lesions is predominantly solid and a peripheral subpleural location or
polygonal shape or 3D ratio > 1.78
[7]. Option B is the best
response. This combination showed 100% specificity and 60-63% sensitivity.
The concave margin feature has a high sensitivity but a low specificity for
benign lesions. Options A and C are not the best responses. Coarse
spiculation, air bronchogram, satellite lesion, and cavitation do not show a
statistically significant difference between benign and malignant lesions.
Options D and E are not the best responses.
Solution to Question 9
Both benign and malignant lesions may increase in size at follow-up
[8]. Option E is the best
response. Benign lesions that can increase in size include organizing
pneumonia and inflammatory pseudotumor. Malignant lesions rarely regress
without treatment. Option A is not the best response. It may be difficult to
assess lesion growth on follow-up studies, depending on the doubling time of
the lesion. Lesions with a long doubling time have slow growth that may
decrease detection on short-interval follow-up. Options B and D are not the
best response. Morphologic characteristics, combined with a change in lesion
size, improve diagnostic accuracy. Option C is not the best response.
Solution to Question 10
Most small (< 6-8 mm) pulmonary nodules visible on chest radiographs are
diffusely calcified, since most noncalcified nodules of that size are not
usually visible. However, accuracy for the detection of calcification in a
pulmonary nodule is unrelated to nodule size
[4]. Option A is not the best
response. It has been shown that, when tested to evaluate for the presence or
absence of calcification on chest radiographs, radiologists tend to hedge
toward calling the nodule not definitely calcified (presumably to avoid
misdiagnosing a malignancy as benign)
[4]. Thus, radiologists tend to
undercall the presence of calcification. Option B is not the best response. If
a nodule has been stable on thoracic radiographs for more than 2 years, the
current standard of care implies that a benign cause can be presumed. However,
there have been case reports of malignant nodules appearing stable for more
than 2 years, and substantial increases in the volume of small nodules may be
missed. Caution is subsequently recommended, and older radiographs or CT scans
should be pursued in this situation. Option C is not the best response. In one
study with an average nodule size of 13 mm, 7% of nodules determined to be
definitely calcified on chest radiographs were in fact not calcified (and
thereby potentially malignant) on CT
[4]. Option D is the best
response. In that same study, the sensitivity (defined as the likelihood
that a calcified pulmonary nodule will be called calcified) was 50%, and the
specificity (defined as the likelihood that a noncalcified pulmonary nodule
will be called not calcified) was 87%. Option E is not the best response.
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TopAbstractINTRODUCTIONEDUCATIONAL OBJECTIVESREQUIRED READINGRECOMMENDED READINGINSTRUCTIONSReferences |
|---|
1 cm) detected at population-based CT screening for lung cancer:
reliable high-resolution CT features of benign lesions.
AJR 2003; 180:955
-964
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