USMLE Forum - Largest USMLE Community

11. A 38-year-old man is being seen in his physician™s
office after being involved in a car accident.
He now has a vague pain along his right
sternal border, where he crashed into the
steering wheel. On examination, his temperature
is 36.6°C (97.8°F), pulse is 80/min, blood
pressure is 123/75 mm Hg, respiratory rate is
14/min, and oxygen saturation is 99% on room
air. Physical examination is significant for
point tenderness over the right sternal border.
An x-ray of the chest shows no broken ribs but
a single, well-circumscribed pulmonary nodule,
1.5 cm in diameter, located in the left
lower lung field. A search through the patient™s
electronic medical file reveals that he had an
x-ray of the chest taken 2 years ago. The radiology
report from that time reveals that the nodule
was only 0.75 cm in diameter. To characterize
the lesion, a CT scan of the chest is
performed and shows œpopcorn calcification
within the lesion. Which of the following risk
factors most increases the chances of malignancy?
(A) Discrete border
(B) Doubling time
© Nodule diameter of 1.5 cm
(D) Patient age
(E) œPopcorn calcification

BBB

AAA

B

œPopcorn calcification: Pulmonary hamartomas have little or no malignant potential, and most of them are asymptomatic, but because bronchogenic carcinoma is an important differential diagnosis

11. The correct answer is B. A solitary pulmonary
nodule is defined as a lung nodule, < 3 cm in
size, that is discovered on x-ray or CT scan of
the chest. Solitary pulmonary nodules have a
422 Section I: Organ Systems ¢ Answers
40% chance of being malignant. Review of old
x-rays is crucial because they can give an indication
of the nodule™s doubling time. A doubling
time between 20 and 400 days is more
concerning for malignancy. For example,
small cell cancer doubles every 30 days, adenocarcinoma
doubles every 180 days, and welldifferentiated
cancers have an even longer
doubling time. Benign processes generally
have doubling times that are < 20 days (infection)
or > 450 days (old granulomas). The doubling
time for this patient is not 2 years. On
x-ray of the chest, a pulmonary nodule appears
as a coin-shaped lesion, when in actuality it
is best approximated as a three-dimensional
sphere. Thus, if a calculation is performed for
the volume of the nodule/sphere, we observe
close to an eightfold increase in size. Thus, the
lesion doubled in size three times during the
2-year period, meaning that the doubling time
was 2 years divided by 3, or every two-thirds of
a year (243.5 days).
Answer A is incorrect. Benign nodules tend
to have a smooth, discrete border, while malignant
lesions have an irregular border.
Answer C is incorrect. Nodule size is directly
related to the likelihood of malignancy. Generally,
a nodule > 3 cm diameter significantly increases
the likelihood of malignancy. In one
study, 80% of nodules > 3 cm were malignant
compared with 20% in nodules < 2 cm.
Answer D is incorrect. The likelihood of malignancy
increases with age. In one study, the
chances of a nodule being malignant as a function
of age were 3% (ages 35“39 years), 15%
(ages 40“49 years), 43% (ages 50“59 years),
and 50% in patients > 60 years old. In another
study, nodules in patients > 50 years old had a
65% likelihood of malignancy, whereas those
in patients < 50 years old had a 33% likelihood
of being malignant. Given the patient™s young
age (38 years), doubling time is a much more
likely risk factor for malignancy.
Answer E is incorrect. The presence of certain
patterns of calcification (best seen on CT)
favors the lesion being benign. Such patterns
include œpopcorn calcification, diffuse/homogenous
calcification, central calcification,
and laminated/concentric calcification. However,
the existence of areas of calcification is

thank

thanks