Giant cell tumor of soft tissues: A case report of extra-articular diffuse-type giant cell tumor of the quadriceps

INTRODUCTION: Giant cell tumors of soft tissue (GCTs) are a relatively rare entity. It is a distinct but uncommon group of neoplasms morphologically identical to osseous giant cell tumor. The diffuse type of extra-articular GCT arising within muscle is a rare benign soft tissue tumor with a wide spectrum of clinical presentation. PRESENTATION OF CASE: This article reports a rare case of a 44-year-old woman with a mass arising from her right thigh. MRI showed only a few areas of low T2 signal in a mass that was hyper intense to muscle. Histopathology of this lesion located within the right quadriceps muscle revealed admixture of multinucleated giant cell with mononuclear cells. This patient was treated by surgical resection and followed up for recurrence. DISCUSSION: Diffuse-type GCTs are commonly located in the periarticular soft tissues, but on rare occasions these lesions can be purely intramuscular or subcutaneous and can be challenging to diagnose. Characteristic findings include gradient echo secondary to hemosiderin deposition, and the low signal on T2. CONCLUSION: Because extra-articular diffuse-type GCTs are rare, the differential diagnosis is challenging. The clinical outcomes of diffuse-type GCTs are unclear because of their rarity. Benign clinical course is expected if the lesion is excised adequately.