An interesting case of melanoma with divergent differentiation aberrantly expressing calretinin stain

Abstract

Metaplastic melanoma or melanoma with divergent differentiation is a rare variant of melanoma with a wide spectrum of mesodermal and ectodermal differentiation. This is a case of metaplastic melanoma with aberrant expression for calretinin stain in the chondroid component and malignant cells adjacent to it. The finding of calretinin positivity in melanoma could be useful in diagnosing metastatic metaplastic melanoma. The awareness of the possibility of aberrant calretinin positivity in metaplastic melanoma with chondroid differentiation is critical to avoid a potential pitfall in misdiagnosing metaplastic melanoma as sarcoma or mesothelioma.

Aberrant Expression of Immunohistochemical Markers in Malignant Melanoma: A Review

“…Immunohistochemical stain for calretinin shows nuclear and cytoplasmic staining in mesothelial cells, adipocytes, endometrial stromal cells, ganglion cells, Sertoli cells, and Leydig cells. Aberrant staining for calretinin stain is rare in melanoma [49]. Metaplastic melanoma with aberrant expression of calretinin stain in both the chondroid component and malignant cells adjacent to it was described in one case report.…”

“…Rare incidents of calretinin positive melanoma are reported in epithelioid, pleomorphic, and metastatic melanoma. The awareness of the possibility of aberrant calretinin positivity in metaplastic melanoma with chondroid differentiation is critical to avoid a potential pitfall in misdiagnosing metaplastic melanoma as sarcoma or mesothelioma [49].…”