Spontaneous complex pheochromocytoma in a Fischer 344 rat

A spontaneous complex pheochromocytoma was diagnosed in the adrenal gland o f an aged female Fischer 344 rat. This expansile neoplasm consisted of pheo chromocytoma and areas of ganglioneuroma. The supporting stroma of both neo plastic components contained spindle-shaped cells, which also formed large fascicles. Immunohistochemically, pheochromocytoma cells stained for synapt ophysin and chromogranin, scattered ganglioneuroma cells stained for neurof ilament protein, and the spindle-shaped stromal cells were positive for S-1 00 protein. Special stains demonstrated Nissl substance in the ganglioneuro ma cells and nerve fibers in the fascicles.