Spitz nevus (large spindle cell and/or epithelioid cell nevus). Age-related involvement of the suprabasal epidermis.

The Spitz nevus (large spindle and/or epithelioid cell nevus) is a benign acquired melanocytic tumour found predominantly in children and adolescents. Depending on the architecture (junctional, compound, dermal) and cytology (predominance of spindle or epithelioid cells, or presence of both cell types) several variants have been distinguished. A histological feature occasionally leading to diagnostic difficulties is the involvement of the suprabasal epidermis. The present study details the occurrence of intraepidermal involvement (pagetoid spread, nesting of cells, trans-epidermal elimination) according to the age of the patients. 89 cases of Spitz nevus were reviewed. There were 19 compound Spitz nevi with evidence of epidermal involvement, 56 cases of compound Spitz nevi without evidence of epidermal involvement and 14 cases of dermal Spitz nevi. The epidermal involvement mainly consisted of nesting of nevus cells above the basal cell layer, 9 cases clearly showing evidence of transepidermal elimination of cell nests. Upward spread of single melanocytes (pagetoid spread) was minimal and always associated with nesting or trans-epidermal elimination. The mean age of patients was significantly lower in the group of compound nevi with intraepidermal involvement (7.16 +/- 4.52 years), than in the group of compound nevi without epidermal involvement (13.18 +/- 8.88 years). The age of the latter group was significantly lower than the group of pure intradermal nevi (30.14 +/- 11.25 years). Thus, involvement of the suprabasal epidermis is not a feature of Spitz nevi in adults; in such a case the diagnosis of malignant melanoma should be considered.