Metastatic Solitary Fibrous Tumor of Parapharyngeal Region: A Case Report with Review of Literature

Abstract

Solitary fibrous tumor (SFT) is a rare fibroblastic mesenchymal neoplasm with a low metastatic potential. The parapharyngeal area in the head and neck is one of the rarest subsites. Surgical excision remains the standard of care. The local recurrence rate stands at 4%, while the distant recurrence rate is 7% over a 5-year period. Radiation can be used in adjuvant, metastatic, and palliative settings. In metastatic disease, therapeutic options are limited, with the most common regimen used in the first line being a combination of dacarbazine and doxorubicin. With a better understanding of molecular biology, many centers use bevacizumab with temozolomide in the first line. A 50-year-old man underwent a wide excision of a mass in the parapharyngeal region in 2014. Histopathology showed a SFT with negative margins and a low mitotic index. He was under regular follow-up. He presented in January 2024 with abdominal discomfort and distension, fever, cough, and substantial weight loss. Clinically, he had hepatomegaly, lab investigations revealed transaminitis and elevated serum alkaline phosphatase. 18F fluorodeoxyglucose positron emission tomography–computed tomography (18F-FDG PET CT) revealed multiple lung and liver metastases. Ultrasound-guided tru-cut biopsy of the liver lesion with immunohistochemistry (IHC) confirmed metastasis from SFT (positive for signal transducer and activator of transcription 6 and cluster of differentiation 34). He received bevacizumab and temozolomide for four cycles, and a PET CT scan showed progressive disease as per Choi's criteria. Treatment was changed to pazopanib 800 mg once daily as the patient was not keen on intravenous chemotherapy. The patient progressed clinically and radiologically. His programmed death-ligand 1 IHC showed a tumor proportion score of 0%. Next-generation sequencing 75 gene panel could not be done due to low tumor content in the block. The treatment was changed to doxorubicin. He received three cycles of doxorubicin and progressed clinically with deterioration of general health and hence offered the best supportive care. He succumbed to the illness in September 2024.

Keywords

metastatic solitary fibrous tumor - lung and liver metastases - case report - head and neck - parapharyngeal

Patient's Consent

Written consent has been obtained from the patient.

Publication History

Article published online:
30 April 2025

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