Elida Voth, BA1, Steve Serio, MD2, John Gross, MD3, Nicholas Dietz, MD3, Kalyana Nandipati, MBBS2. 1Creighton University School of Medicine, 2Department of Surgery, Creighton University School of Medicine, 3Department of Pathology, Creighton University School of Medicine
Solitary fibrous tumors (SFT) are uncommon fibroblastic mesenchymal neoplasms that display a wide range of histologic behaviors. These tumors, which are estimated to account for 2% of all soft tissue neoplasms, typically follow a benign clinical course. However, it is estimated that 10-30% of SFTs are malignant and demonstrate aggressive behavior with local recurrence and metastasis up to several years after surgical resection. We report a case of SFT arising from the stomach, which is an exceptionally rare finding and has been reported only six times in the literature. Additionally, this tumor was associated with dedifferentiation into undifferentiated pleomorphic sarcoma. To our knowledge, there are no documented cases of a malignant SFT arising from the stomach to demonstrate dedifferentiation into an undifferentiated pleomorphic sarcoma.
A 68-year-old male presented to the emergency department with vague complaints of right-sided flank pain. The patient had a history of nephrolithiasis and underwent a CT abdomen. This scan revealed a large heterogeneous mass in the left upper quadrant. The patient underwent endoscopic ultrasonography with fine needle aspiration of the mass, which stained strongly for CD34. Gastrointestinal stromal tumor (GIST) was the favored diagnosis as it is by far the most common mesenchymal neoplasm of the stomach, especially CD34 positive spindle cell neoplasm. Accordingly, the patient began treatment with imatinib; however, after four weeks of therapy, there was no significant radiologic regression. A second biopsy was performed and the specimen was sent for STAT6 immunohistochemistry, which revealed diffuse strong nuclear positivity. A diagnosis of solitary fibrous tumor was provided. Surgical resection of the tumor was performed, which measured 17x14x10.5 cm. The patient was to undergo surveillance imaging every 3 to 6 months post-operatively. Surveillance scan showed solitary metastatic disease in the left lateral segment of the liver. He underwent left lateral segmentectomy with an uneventful recovery.
Our case was complicated by diagnostic dilemma with GIST, highlighting the challenges of diagnosing and characterizing SFTs. Dedifferentiation, or the abrupt transition from a classic SFT into a high-grade sarcoma, is a particularly concerning finding in our case, as it is associated with a worse prognosis than classic malignant SFT. The STAT6 marker by immunohistochemistry is very specific for SFT and may have aided in the diagnosis earlier. Therefore, it is imperative to keep solitary fibrous tumor, albeit exceedingly rare, in the differential diagnosis of mesenchymal neoplasms of the stomach.
Presented at the SAGES 2017 Annual Meeting in Houston, TX.
Abstract ID: 85039
Program Number: P155
Presentation Session: iPoster Session (Non CME)
Presentation Type: Poster
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