P0120 - Solitary but Not Silent: When a Pancreatic Mass Reveals a Rare Diagnosis

Clarimar Diaz-Lopez, MD¹, Jinye Liu, DO², Rami Basmaci, MD², Abdulazeez Swaiti, MD², Christin Wilkinson, MD², Sarah RT. Jahangir, MD³, Deniz Coskuner, MD³, Christina Santana, MD², Stephanie Ibarra Lepe, MD², Saeed S. Graham, MD⁴, Hassam Ali, MD⁵, Kara Regan, MD⁵
1East Carolina University Medical Center, Greenville, FL; 2East Carolina University Medical Center, Greenville, NC; 3ECU Health Medical Center, Greenville, NC; 4ECU Department of Internal Medicine, Greenville, NC; 5East Carolina Gastroenterology, Greenville, NC

Introduction: Solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms, most often arising in the thoracic cavity, with approximately 20% found in the abdominal cavity. Pancreatic involvement is infrequent, with only a few reported cases. Unlike thoracic SFTs, pancreatic SFTs show no sex predilection and are typically present around age 60, most often in the pancreatic head. These tumors are usually discovered incidentally or during the evaluation of vague abdominal symptoms and rarely with obstructive jaundice. Diagnosis can be difficult due to nonspecific imaging features and overlap with other pancreatic tumors. Most are diagnosed after surgical resection, although endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) has rarely been reported as a diagnostic method. We report a rare case of pancreatic SFT diagnosed by EUS-FNA.

Case Description/

Methods: An 87-year-old male with atrial fibrillation presented with abdominal pain, belching, and bloating. A CT revealed a lobulated mass with low attenuation, suggesting necrosis, arising from the pancreatic head and extending into the mesentery, compressing the duodenum without invasion. EUS showed a large, rounded, heterogeneous lesion with central necrosis and prominent vascularity. FNA was performed; the rest of the pancreas appeared normal. Histology showed spindle cell proliferation. Immunohistochemistry (IHC) was positive for STAT6, CD99, and Bcl-2, confirming the diagnosis of SFT. The patient declined surgery and opted for oncology surveillance.

Discussion: This case of a rare pancreatic SFT diagnosed via EUS-FNA, is among the few cases reported in the literature using this method. Although imaging lacks pathognomonic features, CT and EUS may reveal findings such as a well-defined hypervascular mass with central necrosis. STAT6 is a key IHC marker supporting diagnosis; CD99 and Bcl-2 may be present but are non-specific. SFTs are called “great simulators” due to variable presentation and nonspecific imaging. Evidence for managing pancreatic SFTs is limited due to rarity, though surgical resection is typically preferred. A 2023 review of nine resected cases reported no recurrence over a 76-month mean follow-up. The malignant potential has been linked to older age, large tumor size, increased cellularity, mitotic activity, necrosis, and infiltrative borders in SFTs from different locations. Given the limited understanding of malignant potential in this location and absence of surgical resection, close surveillance was recommended for our patient.


Figure: Figure 1: Contrast-enhanced CT of the abdomen and pelvis demonstrating a pancreatic solitary fibrous tumor (SFT) indicated by the red arrow measuring 7.8 x 7.0 cm in axial dimension. The lesion appears as a well-circumscribed, mildly lobulated, heterogeneous mass with areas of low attenuation suggestive of necrosis in the right mid to upper abdomen. (A) and (B) represent axial and coronal views at different levels respectively.


Figure: Figure 2: (A) Histologic section showing a pancreatic solitary fibrous tumor with a hyalinized area. Hematoxylin and eosin (H&E) stain, et al. World J Gastrointest Surg. 2016;8(6):461–6. (B) STAT6 positivity in SFT infiltrating pancreatic parenchyma, et al. J Am Soc Cytopathol. 2020;9(4):272–7.

Disclosures:
Clarimar Diaz-Lopez indicated no relevant financial relationships.
Jinye Liu indicated no relevant financial relationships.
Rami Basmaci indicated no relevant financial relationships.
Abdulazeez Swaiti indicated no relevant financial relationships.
Christin Wilkinson indicated no relevant financial relationships.
Sarah Jahangir indicated no relevant financial relationships.
Deniz Coskuner indicated no relevant financial relationships.
Christina Santana indicated no relevant financial relationships.
Stephanie Ibarra Lepe indicated no relevant financial relationships.
Saeed Graham indicated no relevant financial relationships.
Hassam Ali indicated no relevant financial relationships.
Kara Regan indicated no relevant financial relationships.

Clarimar Diaz-Lopez, MD¹, Jinye Liu, DO², Rami Basmaci, MD², Abdulazeez Swaiti, MD², Christin Wilkinson, MD², Sarah RT. Jahangir, MD³, Deniz Coskuner, MD³, Christina Santana, MD², Stephanie Ibarra Lepe, MD², Saeed S. Graham, MD⁴, Hassam Ali, MD⁵, Kara Regan, MD⁵. P0120 - Solitary but Not Silent: When a Pancreatic Mass Reveals a Rare Diagnosis, ACG 2025 Annual Scientific Meeting Abstracts. Phoenix, AZ: American College of Gastroenterology.