Multifocal micronodular pneumocyte hyperplasia in a postmenopausal woman with tuberous sclerosis

We report a peculiar case of multifocal micronodular pneumocyte hyperplasia (MMPH) without association of pulmonary lymphangioleiomyomatosis (LAM) in a 56-year-old postmenopausal woman with tuberous sclerosis. This case is su rmised to be a forme fruste of tuberous sclerosis, Computed tomography demo nstrated multiple micronodules, measuring up to 5 mm in size, present in th e bilateral lung fields, but no cystic changes. A proliferation of pleomorp hic type-II pneumocytes lining the thickened alveolar septa in an adenomato id pattern, with an associated increase in alveolar macrophages, was observ ed without typical nuclear atypia. In fully developed lesions, the ingrowth of more proliferating type-II pneumocytes into the thickened alveolar sept a and macrophages filling the alveolar lumens were characteristic findings. Proliferation of immature smooth muscle cells suggesting LAM was not obser ved. Positive immunohistochemical stains for cytokeratin, epithelial membra ne antigen, and surfactant apoproteins A and B, and negative staining for H MB45, alpha-1 smooth muscle actin, desmin, and carcinoembryonic antigen con firmed the characteristics of alveolar lining cells in each MMPH lesion. MM PH associated with tuberous sclerosis in the postmenopausal woman appears t o be similar to that described in premenopausal women. The present case is familial rather than sporadic and suggests no relationship between the deve lopment of MMPH and the underlying hormonal state.