A rare case malignant granular cell tumor of the thigh with radiological imaging likely rhabdomyosarcoma: A case report

Granular cell tumors (GCTs) are uncommon soft tissue tumors characterized by the cytoplasmic granular appearance of the neoplastic cells. Malignant GCTs are rare neural tumors, intensely aggressive. Both the rare occurrence of malignant GCTs and its similarities in features with their benign lesions make the diagnosis of this malignancy difficult. Malignant GCTs comprise less than 2% of GCTs and are mostly found in the subcutaneous soft tissues of the lower extremities, especially the thighs. This article presents a case of a large malignant GCTs in the left thigh of a 46-year-old woman. Plain radiograph of the left thigh demonstrated a soft tissue mass without bone involvement. MRI images showed a malignant solid mass 7.8 x 5.2 x 21.6 cm, with ill-defined border, irregular edges, and suspected rhabdomyosarcoma. Incisional biopsy of the mass lesion revealed mixed epithelioid and spindle tumors, suspected malignant GCTs. Histological examination performed by a musculoskeletal pathologist, demonstrated nests and sheets of epithelioid to polygonal cells with hyperchromatic, intensely eosinophilic granular cytoplasm, prominent nucleoli, increased mitotic activity, necrosis, areas of spindling with significant atypia, and positive for S100 by immunohistochemistry. In conclusion, this patient with malignant soft tissue tumor demonstrated polygonal and spindle cells with eosinophilic granular cytoplasm, which need to be considered diagnosed as Malignant GCTs. This case stresses the importance of thorough histological examination in the diagnosis of malignant GCTs.