THE INTERMEDIATE FILAMENT PERIPHERIN IS EXPRESSED IN CUTANEOUS MELANOCYTIC LESIONS

Peripherin is an intermediate filament involved in growth and developm ent of the peripheral nervous system and is localized to neurons, some other cells derived from neural tube and neuraI crest, and some neuro endocrine cells (e.g. beta cells of islets of Langerhans). Peripherin also has been demonstrated in neuroblastomas and cutaneous neuroendocr ine (Merkel cell) carcinomas. The expression of peripherin by other ce lls derived from the neural crest is unknown. We evaluated by immunohi stochemistry 74 cutaneous melanocytic lesions including primary invasi ve malignant melanoma (IMM), melanoma in situ (MIS), atypical nevus (n evus with architectural disorder and cytologic atypia of melanocytes) (AN), spindle and epithelioid cell nevus (Spitz nevus) (SN), blue nevu s (BN), and common intradermal benign melanocytic nevus (BMN) for expr ession of peripherin. Peripherin was detected in a cytoplasmic distrib ution within tumor cells in 14/14 IMM and 8/10 MIS. For IMM, peripheri n localized to both the intraepidermal and invasive dermal components. Peripherin was detected in 10/10 AN and 9/9 SN, being localized to th e intraepidermal component and, focally, to the superficial dermal com ponent of the lesions. The dendritic nevus cells in 15/15 BN also expr essed peripherin. For most of the BMN, expression of peripherin was ab sent or limited to rare, scattered cells in the superficial portion of the lesions. Melanocytes in adjacent normal skin were not labeled in any of the lesions studied. These results indicate that expression of peripherin is common in both benign and malignant melanocytic lesions, but not in normal resting adult melanocytes. Among benign lesions, ex pression of peripherin in the dermal component is rare except in the d endritic cells of BN. These findings provide evidence that the express ion of peripherin, a marker of neuronal differentiation, is maintained by IMM, MIS, and BN, but is lost in the normal maturational sequence of the dermal component of other melanocytic lesions.