Almost all small pulmonary nodules detected by chest x-rays are benign or false-positive findings

Most pulmonary nodules smaller than six mm detected on chest x-rays are either benign or later revealed to be false-positive findings by a CT exam, according to a new study published in Clinical Radiology

“The evaluation of a patient with a pulmonary nodule is a common diagnostic dilemma, as some of these nodules may be malignant,” wrote author Matheus Zanon of the department of radiology at Pavilhão Pereira Filho Hospital in Porto Alegre, Brazil, and colleagues. “CT is considered the reference standard to characterize pulmonary nodules, considering characteristics such as size, borders, location, presence of fat, calcifications, and stability over time.”

The authors examined more than 200 non-oncological patients who underwent chest CT after a chest x-ray revealed a pulmonary nodule. The average time between the x-ray and chest CT was 40 days, though the interval ranged from zero to 176 days. Overall, 95.5 percent of nodules smaller than six mm were benign or not present at CT. More than 81 percent of nodules six mm or larger were benign or not present at CT.

“These results,” the authors wrote, indicate that nodules smaller than six mm detected on chest x-rays “most likely represent a benign finding.”

Zanon et al. noted that their study did have limitations, including the relatively small sample size and the fact that these patients came from a population known for granulomatous diseases.