Primary malignant solitary fibrous tumor of the neck in an HIV-positive patient: a case report.

We report a rare case of malignant solitary fibrous tumor (MSFT) in the cervical region presenting with aggressive bone destruction and lung metastasis in a 54-year-old HIV-infected male. The patient, who was on long-term antiretroviral therapy (EFV + 3TC+TDF), presented with a 5-month history of a progressively enlarging mass in the posterior neck (approx. 10.0 cm x 8.0 cm x 4.0 cm) accompanied by radiating pain in the right upper limb. Initial imaging revealed an osteolytic, destructive lesion involving the C3-C5 vertebrae and multiple solid pulmonary nodules, suspicious for malignancy. Preliminary biopsy and immunohistochemistry initially suggested a mesenchymal malignant tumor, possibly a BCOR-altered sarcoma. Following a multidisciplinary team (MDT) consultation and according to the 2024 CSCO guidelines for bone and soft tissue tumors, the patient received two cycles of neoadjuvant chemotherapy (Epirubicin 30mg D1-D3 and Ifosfamide 2g D1-D5). Subsequent surgical resection was performed, and definitive histopathological and immunohistochemical analysis of the postoperative specimen confirmed MSFT (STAT6+, CD34+, P53 mutant type ~85%, and Ki-67 ~60%). This case emphasizes the diagnostic challenge of differentiating rare spindle cell sarcomas in HIV-infected patients; high-grade MSFT can mimic other aggressive sarcomas, and comprehensive postoperative pathological evaluation, especially STAT6 staining, is essential for definitive diagnosis and tailoring oncological management.