FUSOCELLULAR GONADAL STROMAL TUMOR OF THE TESTIS WITH EPITHELIAL AND MYOID DIFFERENTIATION

We describe an unusual fusocellular gonadal stromal tumour with a beni gn behaviour in the left testis from a 16-year-old man. The neoplasm c onsisted of a non-encapsulated proliferation of irregularly arranged, fusiform cell bundles in fibrous connective tissue. The tumour cells c ontained a slightly infolded nucleus, some dilated rough endoplasmic r eticulum cisternae, abundant filament bundles which connected to subpl asmalemmal electron-dense bodies, pinocytotic vesicles and a discontin uous basal lamina, The intercellular spaces were narrow and the tumour cells were joined by desmosomes. These cells were immunoreactive for muscle actin, alpha-actinin and vimentin, Focal immunostaining for col lagen type IV was observed around the cells, No immunoreactivity for k eratins, desmin S-100 protein or XIIIa factor was found, The findings suggest that the tumour arose from the peritubular myoid cells.