FDG PET/CT Evaluation of a Giant Orbital Hemangiopericytoma with Maxillary Involvement in a 58-Year-Old Indian Female: A Rare Case Report

Hemangiopericytomas (HPCs), recently reclassified under solitary fibrous tumors (SFTs), are rare mesenchymal neoplasms of vascular origin. Involvement of the orbit is exceptionally uncommon. We present the case of a 58-year-old Indian woman with a known history of orbital HPC who underwent debulking surgery 2 years back. She presented with progressive swelling of the left hemiface, worsening over the last month. Clinical evaluation revealed proptosis, lagophthalmos, corneal xerosis, and bluish discoloration over a firm maxillary mass. Contrast-enhanced computed tomography (CT) revealed a large soft tissue mass involving the left maxilla, with extension into the orbit and nasal cavity. Fluorodeoxyglucose (FDG) positron emission tomography/CT (PET/CT) was performed for metabolic characterization, extent delineation, and to rule out metastasis. It demonstrated a large lobulated lesion in the left maxillary and orbital region measuring 7.5 × 6.2 × 5.8 cm, with intense FDG uptake (maximum standardized uptake value 10.2), correlating with high-grade feature, Ki-67 of 50, but no evidence of distant spread. Histopathology showed spindle-shaped tumor cells with a “staghorn” vascular pattern. Immunohistochemistry was positive for CD34 and STAT6, confirming the diagnosis of HPC. The patient underwent complete surgical excision with orbital reconstruction and remains recurrence-free at 6 months. HPCs, though histologically benign in some cases, may behave aggressively, and early detection, staging, and follow-up with appropriate imaging are essential. This case demonstrates the utility of 18F FDG PET/CT in assessing metabolic activity, delineating total tumor burden, and ruling out distant metastases in orbital SFT/HPCs. Although structural imaging is required for local surgical mapping, metabolic imaging provides complementary prognostic information by reflecting cellular proliferation (Ki-67) and staging the systemic tumor burden.