A case of micronodular pneumocyte hyperplasia diagnosed through surgical resection.

Micronodular pneumocyte hyperplasia (MNPH) is often associated with tuberous sclerosis complex and/or lymphangioleiomyomatosis. We present the case of a 45-year-old woman with MNPH without evidence of either. A preoperative high-resolution chest computed topographic scan demonstrated a ground-glass opacity 8 mm in diameter that revealed the possibility of atypical adenomatous hyperplasia (AAH) or bronchioloalveolar carcinoma (BAC). Therefore an S3 segmentectomy of the right lung was performed, and the specimens revealed the characteristic histological and immunohistological features of MNPH. Solitary MNPH is extremely rare and requires to be distinguished from AAH or BAC on a computed tomographic scan; therefore surgical resection may be required to definitely rule out malignancy.