[High-resolution CT findings of pulmonary atypical adenomatous hyperplasia of 5 mm or less in diameter].

OBJECTIVE: To clarify the high-resolution CT(HRCT) findings of pulmonary atypical adenomatous hyperplasia (AAH) of 5 mm or less in diameter.
MATERIALS AND METHODS: We evaluated the HRCT findings of 43 histopathologically confirmed AAH of 5 mm or less in diameter in 7 patients who underwent lobectomy for pulmonary adenocarcinoma. For comparison, we also examined the HRCT findings of 13 bronchioloalveolar carcinomas (BAC) of the same size from these patients.
RESULTS: We identified 36 of 43 AAH and all 13 BAC on HRCT performed with multidetector-row CT. Thirty-five AAH and 11 BAC showed ground-glass opacity without any high-attenuation component. Margins of 20 AAH were well defined, and 16 were ill defined. In BAC, 11 lesions demonstrated well-defined margins, with only 2 showing ill-defined margins.
CONCLUSION: Most AAH lesions of 5 mm or less in diameter are identified as ground-glass opacity on HRCT. Detection of minute ground-glass opacity is important in locating AAH on HRCT.