Immunohistochemical CD10 Expression is Useful for Differentiating Malignant Melanoma from Benign Melanocytic Nevus

Abstract

Malignant melanoma (MM), an aggressive skin neoplasm, can be difficult to differentiate histologically from benign melanocytic nevi (BMN). Although immunohistochemical analysis could facilitate diagnosis of MM, markers that discriminate between benign and malignant lesions have not yet been established. However, CD10 expression is associated with MM progression. We immunostained 36 MM and 50 BMN specimens for CD10 to evaluate whether CD10 immunostaining could distinguish between BMN and MM tumors. In the 36 MM samples, we found CD10 expression in 17 (47.2%) sample tumor cells and 32 (88.9%) stromal cells, for 34 of the 36 MM specimens (94.4%) overall. In contrast, no BMN (0/50) samples had CD10⁺ tumor cells, although a few (8/50, 16.0%) showed stromal staining. The two specimen types thus significantly differed in CD10 expression (P<0.01), indicating that melanocytic CD10⁺ tumor cells are likely to be malignant. Also, melanocytic stromal cells with diffuse, strong CD10 expression are more likely to be malignant than those with light, focal CD10 expression. Although hematoxylin and eosin staining is fundamental to the diagnosis of melanocytic lesions, CD10 immunostaining may help distinguish between BMN and MM.