MALIGNANT FIBROUS HISTIOCYTOMA WITH GRANULAR CELLS, MIMICKING A GRANULAR CELL TUMOR: Light, Electron Microscopic and Immunohistochemical Observation of a Case

The tumor that occurred subcutaneously in the left hypochondriac region of an 87-year-old female is reported. Light microscopically, this tumor was composed of two kinds of cells, spindle cells and granular cells. The spindle cells showed various pictures such as fascicular arrangement, pleomorphic giant cells in the myxoid stroma and areas with abundant blood vessels. The granular cells contained PAS positive and diastase-resistant granules, and these granules, being electron microscopically phagocytic lysosomes, showed the same findings as the granules seen in the granular cell tumor. The immunohistochemical studies for S-100 protein, neuron specific enolase, CEA, myoglobin, and lysosome were negative, but α-antichymotrypsin was positive. From the microscopic and immunohistochemical findings, this tumor was diagnosed as a malignant fibrous histiocytoma with granular cell changes of tumor cells. ACTA PATHOL. JPN. 35 : 1555–1560, 1985.