Clusterin expression in primary and metastatic melanoma

Clusterin is a pleiotrophic glycoprotein that has been implicated in diverse physiologic processes. Recent studies of gene expression profiling found clusterin to be expressed in desmoplastic variants of malignant melanoma. In this study, we extended those observations and examined clusterin expression in a larger number of primary as well as in metastatic melanomas and melanocytic nevi. We used tissue microarray panels as well as selected conventional sections from formalin-fixed and paraffin-embedded tissue blocks. Positive staining for clusterin was found in seven of 21 (30%) primary desmoplastic and three of 21 (7%) non-desmoplastic melanoma. Among metastatic tumors, clusterin expression was found in five of 37 tumors (13.5%). Clusterin expression was not seen in melanocytes of normal skin or in any of the 10 melanocytic nevi tested. Clusterin expression was not entirely restricted to melanoma; it was also seen in a few non-neoplastic tissues, including perifollicular fibroblasts, occasional sebocytes, and the epithelial cells lining sebaceous duct and the isthmus of the hair follicle. Our findings confirm the observation that clusterin can be expressed in melanoma, in particular primary desmoplastic melanoma. However, clusterin appears to be present only in a minority of melanomas.