S5729 Primary Hepatic GIST: Rare Tumor Defying Conventional Origins – A Case Report With Radiological-Pathological Correlation

Introduction: In clinical practice, occasionally one encounters cases that defy textbook descriptions. This holds particularly true for stromal tumors developing outside their usual anatomical boundaries. This patient's situation especially is noteworthy given both the radiological progression and the surgical/pathological confirmation of a tumor. Serial imaging shows an unusual metamorphosis from fluid-filled cyst to solid tumor mass over sixteen months; a progression pattern rare for liver based gastrointestinal stromal tumors (GISTs). It was through surgical exploration and pathological examination, that we were able to confirm the tumor's origin within liver tissue rather than secondary spread. Case Description/Methods: Our case involves an 82-year-old woman presenting with right upper quadrant pain. Sixteen months prior, a computed tomography scan had shown an innocent-appearing 4.9 cm liver cyst. New imaging now revealing a startling transformation: 8.8 cm solid mass emerging from hepatic segment III. Diagnostic upper endoscopy with endoscopic ultrasound was performed, which showed normal esophageal gastric and duodenal anatomy. endoscopic ultrasound identified a 9 × 6 cm solid, necrotic-appearing mass within the left hepatic lobe, distinct from the gastric wall. Fine-needle aspiration of this lesion confirmed the diagnosis of GIST with no malignant cells detected in EGD gastric biopsies. After surgical resection, the report showed tumor bulk deeply embedded in liver tissue, minimal contact with the stomach's outer surface. Repeat pathology revealed gradual infiltration with entrapped hepatocytes at the periphery, a pattern characteristic of primary hepatic neoplasms. Gastric involvement was limited to reactive changes, without submucosal penetration. Discussion: This case fundamentally challenges the assumption that hepatic GISTs must represent metastases. Serial imaging documenting the lesion developing primarily within the liver for over a year before any gastric contact appeared showed an unlikely progression for a metastatic lesion. Also, histological evidence revealing a growth pattern with hepatic focus and gradual hepatocyte displacement and no gastric submucosa involvement raises multiple questions as to the source of this tumor. The evidence suggests these rare tumors may develop through distinct biological pathways, requiring alternate diagnostic and therapeutic approaches. Most importantly, it serves as a reminder that medical knowledge evolves through rare cases; each one challenging our assumptions and expanding our understanding of disease processes.