Compound clear cell sarcoma misdiagnosed as a Spitz nevus.

Overview

Clear cell sarcoma (CCS) typically presents as a tumor in the deep soft tissue of extremities, but when centered in the dermis it may be confused with a melanocytic nevus, primary nodular or metastatic melanoma. Compound variants of CCS, i.e. tumor cells present in both the epidermis and underlying soft tissue have not yet been described. Herein we report such a case, which initially presented as a nodule on the left wrist of a young woman at 19 years of age. The lesion was then interpreted as 'Spitz nevus, compound type'. Twelve years later the patient noticed an enlarged lymph node in the right axilla. The excised lymph node was nearly completely replaced by malignant tumor cells, which were immunoreactive for S100 protein. They resembled the tumor cells of the wrist lesion. Cytogenetic analysis of the metastatic tumor revealed a t(12;22) translocation. Fluorescence in situ hybridization confirmed Ewing's sarcoma breakpoint region 1 (EWSR1) rearrangement in 70% of the tumor cells, thereby supporting the diagnosis of metastatic CCS. Our case is of interest because it documents that CCS can involve the epidermis. This observation expands the morphological spectrum associated with this tumor.