P2045 - Primary Rectal GIST: A Case Series and Literature Review

Mehwish Kishore, MD¹, Jonathan Ragheb, MD², Matthew Hill, BA¹, Srinivas Puli, MD^1
1University of Illinois College of Medicine, Peoria, IL; ²Cleveland Clinic Florida, Weston, FL

Introduction: Rectal gastrointestinal stromal tumors (rGISTs) are relatively rare, accounting for about 3–5% of GISTs, and originate from the interstitial cells of Cajal. This single-center retrospective case series will discuss the features and evolution in the management of primary rGIST.

Case Description/Methods: We describe 5 patients with primary rGIST over 2012-2020 (Table 1). Four patients presented with abdominal pain and changes in stool caliber, color or frequency; patient#3 was asymptomatic and was found to have a mass during screening colonoscopy. None of the patients had a history of prior malignancy or genetic syndrome. On endoscopic ultrasound (EUS), no lymph node infiltration was noted for any of the patients. For patient #1, an EUS was not performed, and he underwent a resection following a confirmation biopsy. For patient #5, EUS showed hypoechoic mass with irregular borders in mucosal layer. The pathology for all patients was positive for spindle type and specifically CD117+. Four patients underwent resection. For patient #3, endoscopic mucosal resection was successfully performed using a band ligator and hot snare resection technique. The surveillance method was individualized, choosing between imaging and colonoscopy depending on ease of completion. Recurrence was noted in patient#5 after 7 years.

Discussion: Menge el al. found that rGIST was detected incidentally in up to 31% of cases. EUS-guided fine needle biopsy (FNB) allows for tissue sampling and locoregional T and N staging. However, most rGIST lack nodal involvement, as in our group. Palazzo et al. showed that the presence of one of the EUS features—irregular border, cystic changes, and lymph nodes with a malignant pattern—can predict potential malignancy with a sensitivity of 91% and a specificity of 88%. However, it is worth noting that only 3.57% of the cases had rGIST. El Chafic et al. demonstrated better tissue acquisition with EUS-FNB using fork-tip style core needle compared with fine needle aspiration. The poor prognostic factors include size > 5 cm, a mitotic rate > 5/50 HPF, and necrosis within the tumor. The standard curative treatment is resection with histologically negative margins, and adjuvant imatinib can reduce long-term recurrence in high-risk cases. Given the rarity of rGIST, most interval surveillance is individualized; however further research is warranted to identify high-risk tumors for recurrence.


Disclosures:


Mehwish Kishore, MD¹, Jonathan Ragheb, MD², Matthew Hill, BA¹, Srinivas Puli, MD¹. P2045 - Primary Rectal GIST: A Case Series and Literature Review, ACG 2024 Annual Scientific Meeting Abstracts. Philadelphia, PA: American College of Gastroenterology.