Pulmonary angiomatoid fibrous histiocytoma invading the pulmonary vein with intracranial metastasis: a case report.

Pulmonary mesenchymal tumors are extremely rare. Angiomatoid fibrous histiocytoma (AFH) originating in the lungs is particularly uncommon, with clinical manifestations similar to those of lung cancer, which often leads to misdiagnosis. We report the case of a 77-year-old male patient who presented with a left hilar mass following trauma. Imaging revealed a mass resembling lung cancer with bronchial and vascular invasion. Bronchoscopic biopsy and immunohistochemistry confirmed an intermediate-type pulmonary AFH. Because of multiple comorbidities, the patient was not eligible for surgical treatment. Six months later, he developed multiple brain metastases with hemorrhage and edema, indicating a high malignant potential and distant metastatic capability. This case enriches the data on pulmonary AFH in older patients, emphasizing its importance in the differential diagnosis of hilar masses and the associated diagnostic and treatment challenges. Moreover, it highlights the need for early identification and standardized follow-up of incidental pulmonary lesions supported by multidisciplinary collaboration for accurate diagnosis. Given the morphological similarity of pulmonary AFH to various spindle cell tumors, immunohistochemistry and molecular pathology are key to its diagnosis. To the best of our knowledge, this is one of very few reported cases of brain metastasis arising from primary pulmonary AFH, emphasizing its potential aggressiveness. Data accumulation, improved diagnostic and treatment standards, and comprehensive management strategies for older complex patients is required to enhance treatment outcomes and quality of life. This report provides a valuable reference for the clinical spectrum and metastatic mechanism of pulmonary AFH.