Abstract
Malignant melanoma is a common and aggressive skin cancer with a high incidence of metastases. Diagnosis is usually straightforward, based on a combination of histomorphology and immunohistochemistry. However, metastatic melanoma is notorious for its phenotypic diversity and loss of differentiation markers. Through recent developments in diagnostic immunohistochemistry and molecular pathology, several new markers are identified to be of use in confirming melanoma diagnosis, especially in undifferentiated and dedifferentiated cases. Here we report a challenging case of a 59-year-old male with splenic metastatic melanoma which revealed a loss of four diagnostic melanocytic markers including S100, SOX-10, HMB45, and MART-1, but a gain of SOX-11.