A LIGHT-MICROSCOPIC, ULTRASTRUCTURAL AND IMMUNOHISTOCHEMICAL STUDY OFSPINDLE-CELL ADRENOCORTICAL TUMORS OF FERRETS

Twelve adrenocortical tumours with a variable spindle-cell component i n ferrets (six spayed females, three intact females, two castrated mal es, and one intact male) were examined by light microscopy. One tumour with a moderate spindle-cell component was examined ultrastructurally , and three tumours were studied immunohistochemically. Light microsco py revealed a spindle-cell component in the tumours that varied from a few such cells occupying the stroma between packets of adrenocortical cells to cells in such large numbers that they formed almost the enti re substance of the tumour. By light microscopy these spindle cells re sembled smooth muscle cells, and the ultrastructural findings, particu larly the presence of thin contractile filaments, suggested that the s pindle cells were of smooth muscle origin. Immunohistochemical stainin g revealed that the spindle cells were negative for cytokeratins and S -100 protein but positive for smooth muscle actin. Desmin was readily demonstrated in two tumours but not in the other examined. Vimentin wa s variable, generally producing a small to moderate amount of reaction product. (C) 1995 Academic Press Limited