Malignant Granular Cell Tumor of the Shoulder: A case report

ABSTRACT

A malignant granular cell tumor (MGCT) occurred in the left shoulder of a 62-year-old man. The patient underwent wide marginal excision followed by chemotherapy and radiotherapy. A metastatic tumor was identified in the axillary lymph node 22 months after the excision of the shoulder mass. The primary tumor was a poorly circumscribed mass measuring 5 5 4 cm. On cut section, it was a solid mass with yellowish tan color. Histologically, both primary and metastatic tumor consisted of polygonal cells with abundant granular cytoplasm and a vesicular nucleus with a prominent nucleolus. Two to three mitotic figures per ten high power fields at 200 were counted. Tumor cells were weakly stained with periodic acid-Schiff (PAS) preparation both before and after diastase digestion, and were positive for S-100 protein, neuron-specific enolase (NSE), and vimentin. By electron microscopy, the cytoplasm was filled with numerous autophagolysosomes containing myelin figures, mitochondria, and fragmented rough endoplasmic reticula. Basal laminae and angulated bodies were also noted. These findings suggest schwannian differentiation of this tumor.