Summary: A family of lesions composed of a newly characterized and distictive cell type, called perivascular epithelioid cell (PEC), has been identified. This cell type characteristically shows immunoreactivity with the melanogenesis-marker HMB45. In this review, we summarize the rapidly growing data on this cell type and its related lesions. These lesions can occur in many different organs, are closely related lo the tuberous sclerosis complex, and can show loss of heterozygosity in TSC1 or TSC2 regions. These lesions include: angiomyolipoma (AML) and its monotypic variants (leiomyoma-like AML, lipoma-like AML, oncocyloma-like AML, monolypic epithelioid AML), pulmonary and extrapulmonary clear cell "sugar" tumor, lymphangiomyoma, lymphangioleiomyomatosis, and renal capsuloma
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