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.
Granular cell tumor is characterized by large eosinophilic cells with granular appearances. These are mostly benign.
Approximately 1~2% are malignant, and establishment of reliable criteria for diagnosing malignant granular cell tumor has been difficult to establish because of the rarity.
Reports on the cytologic features of this neoplasm are hardly found in Korea. We report a case of rarely-occurring granular cell tumor in the lower leg of a 40-year-old male, diagnosed on fine needle aspiration cytology, together with a review of the literature regarding significant adverse histology and prognostic factors. The aspirates revealed cellular smears of isolated cells, syncytial clusters, and occasionally stripped nuclei in a fine, bluish-purple, granular background. Tumor cells were polygonal, rounded, or slightly spindled, and showed ill-defined granular cytoplasm. Nuclei were small and round or oval, with inconspicuous or small, prominent nucleoli. The nuclei showed rare intranuclear cytoplasmic invagination.
Occasionally, there were mild to moderate nuclear pleomorphisms with vesicular nuclei, with large, prominent nucleoi, but no mitosis. The immunocytochemical stain for S-100 was strongly positive in the cytoplasm of tumor cells with occasional nuclei.