Pulmonary Metastases from a Hemangiopericytoma/Solitary Fibrous Tumor Spectrum Neoplasm in a Patient with a Poorly Documented Thigh Tumor: A Case Report

Background and Clinical Significance: Solitary fibrous tumor (SFT), historically termed hemangiopericytoma (HPC), is a rare fibroblastic mesenchymal neoplasm with variable biological behavior. Pulmonary involvement is uncommon and may represent either a primary thoracic tumor or metastatic disease from an extrapulmonary site. Its clinical course ranges from indolent, surgically curable disease to aggressive malignancy with local recurrence and distant dissemination. In this retrospective case, confirmatory STAT6 immunohistochemistry was unavailable; therefore, the tumor is described as a hemangiopericytoma/solitary fibrous tumor spectrum neoplasm. Case Presentation: We report the case of a 33-year-old woman who presented with sudden-onset hemoptysis and was found to have two large, well-defined bilateral pulmonary masses. Initial clinical and radiological evaluation raised suspicion of primary pulmonary tumors or other benign lesions. Because both lesions were considered resectable, staged pulmonary resections were performed. Subsequent reassessment of the patient’s medical history revealed previous surgeries for a poorly documented recurrent thigh tumor, later confirmed to represent the primary malignant hemangiopericytoma/solitary fibrous tumor spectrum neoplasm. Despite staged pulmonary resections, systemic chemotherapy, and further oncologic management, the disease progressed rapidly, with cerebral, bilateral pulmonary, mediastinal, and subcutaneous metastases. The patient died within 18 months of the initial pulmonary diagnosis. Conclusions: This case highlights the diagnostic difficulty of metastatic pulmonary hemangiopericytoma, particularly when the primary soft tissue tumor is inadequately documented. It emphasizes the importance of detailed clinical history, retrieval of previous histopathological reports, and long-term surveillance in patients with soft tissue tumors, even when initially considered benign.