Solitary fibrous tumor of the stomach

• Published in: American journal of clinical pathology Vol. 162; no. Supplement_1; p. S41
• Main Authors: Aslam, Sumayya, Chandan, Vishal S, Shah, Sejal S, Aslam, S, Chandan, V S, Shah, S S
• Format: Journal Article
• Language: English
• Published: 15-10-2024
• ISSN: 0002-9173; 1943-7722
• DOI: 10.1093/ajcp/aqae129.089

Abstract Introduction/Objective Solitary fibrous tumor (SFT) is an uncommon fibroblastic tumor that originates from the mesenchymal tissue. It has been rarely reported within the stomach. None of these reported tumors have occurred in a background of autoimmune atrophic gastritis as was seen in our patient. Methods/Case Report Case report Results (if a Case Study enter NA) An 85-year-old female with history of anemia and autoimmune atrophic gastritis presented with two-month history of dysphagia and abdominal discomfort. Upper gastrointestinal endoscopy showed a 1 cm subepithelial lesion in the gastric body along the greater curvature. Upper endoscopic ultrasound showed mildly hypoechoic lesion in the submucosa of the stomach with the differential of leiomyoma, neuroendocrine tumor, gastrointestinal stromal tumor, and an atypical looking lipoma. The entire gastric lesion was lifted with submucosal saline injection and then resected using cap endoscopic mucosal resection (EMR) snare cautery. Gross examination showed a well-circumscribed lesion with firm, tan-white cut surface. On microscopy, a bland appearing spindle cell proliferation within a collagenous stroma was seen with alternating hypercellular and hypocellular areas and few dilated vessels. No significant mitosis, nuclear pleomorphism or necrosis was identified. Immunohistochemical stains were performed and the lesional cells were positive for STAT6. Markers for gastrointestinal stromal tumor (CD117, DOG1), smooth muscle tumor (desmin, smooth muscle actin) and schwannoma (S100, SOX10) were negative. Nuclear staining for STAT6 is a sensitive and specific marker for SFTs. This particular SFT was considered to be of low risk and non-malignant considering its small size, lack of mitotic activity and tumor necrosis. The etiology for SFT is not entirely clear but molecular studies have shown that the NAB2::STAT6 translocation in a spindle cell neoplasm is a diagnostic hallmark for SFTs. Conclusion Solitary fibrous tumors have been rarely reported within the stomach. Complete surgical resection with negative margins is the mainstay of treatment as they may recur after an incomplete resection.