Diffuse-Type Tenosynovial Giant Cell Tumor of the Hip With Acetabular Bone Involvement: A Case Report With Radiologic-Pathologic Correlation.

backgroundDiffuse-type tenosynovial giant cell tumor (D-TGCT) is an uncommon synovial neoplasm. Hip involvement is rare and may be difficult to recognize because symptoms are nonspecific and osseous erosion can mimic more aggressive infectious, inflammatory, or neoplastic processes. We report a case of hip D-TGCT that presented as an erosive acetabular lesion and required histopathologic and immunohistochemical confirmation. CASE: A 56-year-old man presented with acute right hip pain and restricted motion after a recent febrile illness that had partially improved following empirical intravenous cefuroxime therapy. Magnetic resonance imaging (MRI) demonstrated diffuse intra-articular synovial proliferation with heterogeneous low-to-intermediate signal intensity on T1-weighted images, heterogeneous signal intensity on T2-weighted images, and heterogeneous enhancement after contrast administration. Computed tomography (CT) showed joint effusion and thinning and erosion of the anterior and inferomedial acetabular wall, whereas plain radiographs were unremarkable. Because the imaging and laboratory findings were inconclusive, the patient underwent surgical excision and synovectomy, curettage of the eroded acetabular wall, alcohol ablation, and autologous iliac bone grafting. Histopathologic examination demonstrated mononuclear cells, osteoclast-like multinucleated giant cells, foamy histiocytes, chronic inflammatory cells, and abundant hemosiderin deposition. Integration of the characteristic morphology, diffuse intra-articular growth pattern, imaging findings, and supportive immunohistochemistry established the diagnosis of D-TGCT. Microbiologic cultures were negative. No postoperative radiotherapy was administered. At the 6-month follow-up, the patient reported sustained pain relief and improved hip motion, although mild restriction of motion persisted.

conclusionHip D-TGCT should be considered when an intra-articular hip lesion shows synovial proliferation with acetabular erosion, even when inflammatory findings raise concern for alternative diagnoses. Magnetic resonance imaging and computed tomography are complementary for defining soft-tissue extent and osseous involvement, but definitive diagnosis depends on clinicopathologic correlation. This case highlights the diagnostic value of histopathology and immunohistochemistry in destructive-appearing hip lesions.