Journal of Oncology Case Reports Online | Volume 2, Issue 1 | Case Report | Open Access
Saqib Ahmed*
Brijesh Thakur1, Saqib Ahmed2, Supreet Kaur3, Seema Acharya4, Aatish Saraswat5
Department of Pathology, Shri Guru Ram Rai Institute of Medical & Health Sciences, Dehradun, Uttarakhand, India
*Correspondence to: Saqib Ahmed
Fulltext PDFBackground: Synchronous occurrence of colorectal adenocarcinoma and gastrointestinal stromal tumour (GIST) is uncommon. The incidental identification of a small spindle-cell lesion in a colorectal resection specimen can create a diagnostic challenge and requires distinction from other gastrointestinal mesenchymal neoplasms. We describe a patient with rectal adenocarcinoma and an incidental small colonic-wall GIST identified at definitive surgery, followed by early local recurrence of the rectal adenocarcinoma.
Case Presentation: A 70-year-old man presented with a rectal mass and significant weight loss. Endoscopic biopsy demonstrated moderately differentiated rectal adenocarcinoma. He received long-course neoadjuvant chemoradiotherapy with capecitabine and subsequently underwent ultra-low anterior resection with coloanal anastomosis and diverting ileostomy. The resection specimen showed a residual approximately 3-cm moderately differentiated adenocarcinoma extending through the muscularis propria into perirectal soft tissue, with treatment effect. Proximal, distal and circumferential margins were free of tumour, and all 17 regional lymph nodes were negative, yielding a pathological stage of ypT3N0. A separate approximately 1-cm spindle-cell lesion in the colonic wall showed bland fascicular spindle cells and was positive for CD117 and DOG1, with a Ki-67 index of approximately 1–2% and a mitotic rate of 0–1 per 5 mm [2]. supporting GIST with very low-risk features. The ileostomy was closed in December 2025. In February 2026, an ulceroproliferative lesion developed near the anal verge. Subsequent PET-CT demonstrated intensely FDG-avid circumferential thickening of the lower rectum and anal canal with presacral and mesorectal nodal uptake, without distant FDG-avid disease. Repeat biopsy in July 2026 confirmed recurrent rectal adenocarcinoma.
Conclusion: This case highlights the importance of meticulous examination of colorectal resection specimens for incidental second primary neoplasms and the value of CD117 and DOG1 in characterising small spindle-cell lesions. It also demonstrates that margin-negative, node-negative resection does not eliminate the risk of early local recurrence in rectal adenocarcinoma with residual ypT3 disease after neoadjuvant treatment. Integrated pathological, endoscopic and radiological surveillance is therefore essential.
rectal adenocarcinoma; gastrointestinal stromal tumour; GIST; synchronous neoplasms; CD117; DOG1; local recurrence; case report
Brijesh Thakur, Saqib Ahmed, Supreet Kaur, Seema Acharya, Aatish Saraswat. Synchronous Rectal Adenocarcinoma and Incidental Colonic Gastrointestinal Stromal Tumour Followed by Early Local Recurrence: A Case Report. Jour Onco Case Rep Onl. 2026;2(1):1-7.