MULTIFOCAL MICRONODULAR PNEUMOCYTE HYPERPLASIA - A DISTINCTIVE PULMONARY MANIFESTATION OF TUBEROUS SCLEROSIS

We report a peculiar multifocal micronodular proliferation of pneumocy tes occurring in a 24-yr old woman with tuberous sclerosis and lymphan gioleiomyomatosis. A computed tomographic scan of the chest demonstrat ed multiple minute nodules present throughout both lung fields, Histol ogically, the nodules were well demarcated, measured up to 1.6 mm in d iameter, and were composed of thickened, fibrotic, alveolar septa line d by pleomorphic, type II pneumocytes. Positive immunohistochemical st ains for keratin, BER-EP4, and surfactant, and negative immunohistoche mical staining with an antibody recognizing Clara cells support an epi thelial origin from type II pneumocytes. The absence of immunohistoche mical staining for HMB45 suggests a histogenesis separate than the les ions of lymphangioleiomyomatosis. We failed to detect estrogen or prog esterone receptors in either the lesions of lymphangioleiomyomatosis o r the micronodular proliferations. Recognition of these unique lesions facilitates their distinction from other epithelial proliferations, p articularly atypical bronchioloalveolar cell hyperplasia. This lesion appears to be a distinctive manifestation of tuberous sclerosis. It is probably hamartomatous.