Testicular Stromal Tumor: Ultrastructural, Immunohistochemical, and Gel Electrophoretic Evidence of Epithelial Differentiation

Abstract

A testicular tumor, removed from a 52-year-old man, was composed of uniform spindle cells and abundant interposed collagen, and was histologically diagnosed as a stromal tumor. Electron microscopy revealed cords of cells sometimes surrounded by a basal lamina. Desmosome-like junctions were found between some cells, and immunostaining for desmoplakins was positive. Immunofluorescence studies also showed cytokeratin-positivity in most and vimentin-positivity in some of the tumor cells. The presence of typical simple epithelial cytokeratins of M, 40000, 45000 and 52000 was revealed by the western blotting method.

Cytokeratin positivity in the tumor cells suggests the epithelial nature of this mesenchymal-looking tumor. The tumor might arise from cytokeratin-positive epithelial elements of the testis or its covering mesothelium, but the histogenesis remains unresolved. Our findings suggest that some of the so-called testicular stromal tumors may in fact be of epithelial nature by presenting features typical of epithelial differentiation.

Key Words:

• immunohistochemistry
• cytokeratins
• testicular tumor
• ultrastructure