Malignant Granular Cell Tumor of the Thigh

Malignant granular cell tumor is a rare neural tumor characterized by abundant granular-appearing tumor cells. These tumors account for <2% of all granular cell tumors. Unlike its benign counterpart, a malignant granular cell tumor presents primarily in the lower limb and is notably larger. Both the uncommon occurrence of malignant granular cell tumors and its similarities in feature with their benign counterparts make diagnosis of this particular malignancy difficult. By 1998, Fanburg-Smith et al developed a diagnostic criteria in which granular cell tumors were divided into 3 categories-benign, atypical, and malignant-based on 6 histological characteristics of the tumor: necrosis, spindling, vesicular nuclei with large nucleoli, increased mitotic activity, high nuclear-to-cytoplasmic ratio, and pleomorphism. This article presents a case of a large malignant granular cell tumor in the right thigh of a 69-year-old woman. Gross examination of the mass showed the well-demarcated, tan, white tumor measuring 18.2 cm long and 7.6 cm wide at its largest width. Histological examination of the mass, performed by an oncological pathologist, demonstrated foci of tumor necrosis, scattered apoptotic cells, prominent nucleoli, increased nuclear-to-cytoplasmic ratio, increased mitotic activity, and areas of spindling with significant atypia. To our knowledge, this is the largest reported case of malignant granular cell tumor in the lower limb diagnosed using the histological criteria established by Fanburg-Smith et al. This case stresses the importance of thorough evaluation in instances of atypical granular cell tumor presentations.