P0085 - Solitary Fibrous Tumor of the Pancreas: Really?

Neil R. Jariwalla, MD¹, Nathan Park, MD², Nabil El Hage Chehade, MD³, Alexa Truong, BS¹, Alyssa Y. Choi, MD⁴, Jason Samarasena, MD^5
1University of California Irvine Medical Center, Orange, CA; ²UC Irvine Medical Center, Orange, CA; ³MetroHealth Medical Center, Cleveland, OH; ⁴H. H. Chao Comprehensive Digestive Disease Center, University of California Irvine, Orange, CA; ⁵University of California - Irvine, Orange, CA

Introduction: Solitary fibrous tumors (SFTs) are mesenchymal tumors that most commonly affect the pleural lining of the lung and are usually benign. SFTs of other organs, notably the pancreas, are extremely rare and can be difficult to distinguish from other neoplasms of similar appearance. Here we present the case of a solitary fibrous tumor of the pancreas initially thought to be a neuroendocrine tumor.

Case Description/Methods: A 64-year-old female was referred to our facility after initially presenting to an outside hospital with generalized abdominal pain. Abdominal ultrasound revealed a 1.9 cm complex cystic lesion in the body of the pancreas. The patient underwent an esophagogastroduodenoscopy (EGD) with endoscopic ultrasound (EUS) which revealed a 1.9 cm hypoechoic/anechoic lesion near the body of the pancreas. Fine-needle aspiration was performed on the lesion. Initial cytology was compatible with a low-grade spindle cell neoplasm with CD-34 positive, STAT-6 positive immunohistochemical staining consistent with a solitary fibrous tumor.

The patient then underwent repeat EGD with EUS/FNA approximately two months later for core needle biopsy of the pancreatic lesion. Endoscopy revealed a peripancreatic hypoechoic lesion now 2.5 cm x 2 cm in size and successful FNA was performed. Final cytology revealed a spindle cell neoplasm highly compatible with solitary fibrous tumor given diffusely positive immunohistochemical staining for CD34 and STAT-6.

Discussion: Solitary fibrous tumors (SFTs) are rare mesenchymal tumors that comprise less than 2% of all soft tissue masses. These spindle-cell neoplasms are most commonly encountered in the pleural lining of the lung but may afflict any organ system. SFTs of the pancreas are exceedingly rare with fewer than 30 cases reported as of 2020. SFTs of the pancreas present a diagnostic challenge as they can often present with vague abdominal symptoms or as an incidental finding on ultrasound or CT imaging of the abdomen. Furthermore, pathologic diagnosis is difficult as these tumors can be difficult to differentiate from neuroendocrine tumors. This case highlights the importance of pathologic diagnosis using immunohistochemical staining to elucidate SFTs given their potential for malignant transformation.



Disclosures:


Neil R. Jariwalla, MD¹, Nathan Park, MD², Nabil El Hage Chehade, MD³, Alexa Truong, BS¹, Alyssa Y. Choi, MD⁴, Jason Samarasena, MD⁵. P0085 - Solitary Fibrous Tumor of the Pancreas: Really?, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.