Ileal Gastrointestinal Stromal Tumor (GIST) Masquerading as Primary Ovarian Malignancy: A Diagnostic Pitfall

Abstract

Aims: To highlight an uncommon case of primary ileal Gastrointestinal Stromal Tumor (GIST) mimicking ovarian malignancy, emphasizing the importance of considering GIST in the differential diagnosis of abdomino-pelvic masses for accurate management. Presentation of Case: A 65-year-old woman presented with a six-month history of dull aching pain and a palpable pelvic mass (14-week size). Pre-operative work-up included an elevated CA-125 level (76.2 IU/mL) and CEMRI findings strongly suggestive of an ovarian neoplastic lesion, leading to a provisional diagnosis of ovarian malignancy and preparation for staging laparotomy. Intraoperatively, after lysing extensive adhesions, a large (14 *10 cm) variegated mass was found to be entirely separate from the adnexa, confirmed to be arising from the ileum. Wide resection of the tumor with 10 cm of adjacent small bowel was performed. Discussion: This case underscores the diagnostic challenge of exophytic ileal GISTs, which can descend into the pelvis and cause non-specific marker elevation like CA-125. The critical intraoperative finding of the mass being adnexa-free guided the correct surgical approach. Post-operative histopathology confirmed GIST with strong c-kit (CD117) positivity. Given the high-risk category (size and location), the patient was started on definitive adjuvant therapy with the tyrosine kinase inhibitor, Imatinib Mesylate. Conclusion: GIST is a rare but critical visceral tumor that can precisely mimic ovarian tumors clinically and radiologically. Surgeons must be cognizant of this entity and include it in the differential diagnosis of abdomino-pelvic masses to ensure appropriate resection and subsequent targeted systemic therapy.