EXPRESSION OF PROLIFERATING CELL NUCLEAR ANTIGEN IN SPITZ NEVUS

Background: Epithelioid and spindle cell nevus (ESN; Spitz nevus) is a histologically well-described entity. We hypothesized that the features of ESN may reflect activation by a proliferative stimulus. Objective: Nevocytes and keratinocytes in ESN and control specimens were examined for expression of the proliferation marker, proliferating cell nuclear antigen (PCNA). Methods: Standard immunohistochemical methods were used to examine the expression of PCNA in a series of ESN, other nevi, and malignant melanoma. Results: PCNA was detected in nevocytes in a significant percentage of ESN but not in other nevi. PCNA expression was increased in basilar keratinocytes in ESN when compared with staining of basilar keratinocytes in normal epidermis. In other melanocytic nevi and noninflamed melanoma, PCNA expression in keratinocytes was similar to that in normal control tissue. Conclusion: Increased PCNA labeling in nevocytes and keratinocytes in ESN suggests that a growth stimulus, present within some of these lesions, affects both keratinocytes and nevocytes.