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Lung Lesions: Clues To Help Determine Benign vs Malignant

Lung Lesions: Clues To Help Determine Benign vs Malignant

BALTIMORE--A number of factors can suggest whether a focal pulmonary
lesion is malignant or benign, but no single test affords a quick
answer, and biopsy is usually necessary to make the diagnosis,
said Peter White, Jr., MD, assistant professor of medicine at
Johns Hopkins University.

At a meeting on nuclear medicine sponsored by Johns Hopkins, two
speakers outlined advances in noninvasive imaging of such lesions
via PET scan and somatostatin receptor scintigraphy, while Dr.
White reviewed the lesion characteristics that may suggest malignancy.

A lung cancer goes through 40 doublings of volume in its life
cycle and is not visible until it reaches 1 cm in size, Dr. White
said. At 3 to 4 cm, it has gone through seven eighths of its life

"By the time it reaches 2 cm, the tumor contains 500 million
malignant cells and starts to metastasize," he said. "When
there are that many cells, it's not surprising that a few will
wander off and set up shop somewhere else."

Statistically, the most common sites for lung cancers are in the
upper lobe and in the right lung. "But," Dr. White said,
"finding a lesion in the lower left lung doesn't mean it's
not malignant."

Age is another suggestive factor. Fewer than 1% of malignancies
arise in patients under 30, and fewer than 5% under age 40, so
Dr. White places the crossover point to suspect malignancy at
age 35. Nonetheless, he said, "you can't assume the lesion
is benign on the basis of age alone."

Nor does calcification rule out a tumor, since 2% of lung cancers
are calcified. Lesions with a wall thickness less than 4 mm are
benign 95% of the time, while those with a thickness greater than
16 mm are 84% likely to be malignant. "Anything in between,"
Dr. White said, "calls for a biopsy." As for size and
shape, malignancy is more likely if the lesion is greater than
3 cm, round or oval, has sharply defined edges, and is surrounded
by aerated lung tissue.


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