Recommended Citation
Stevenson JR, Ezeano C, Kaura T. Beyond the Inflamed Segment: Early-Onset Lymphoglandular Complex-Like Ascending Colon Adenocarcinoma After Complicated Sigmoid Diverticulitis. Poster presented at: American College of Gastroenterology (ACG) 2026 Annual Scientific Meeting; October 11, 2026; Nashville, TN. Poster P0417.
Presentation Notes
Poster presented at: American College of Gastroenterology (ACG) 2026 Annual Scientific Meeting; October 11, 2026; Nashville, TN. Poster P0417.
Abstract
Introduction: Colonoscopy is recommended after complicated diverticulitis to exclude malignancy. Lymphoglandular complex-like colorectal carcinoma (LGCC) is a rare, recently characterized variant in which invasive carcinoma is encased by lymphoid stroma, mimicking adenomas with lymphoglandular complexes. We describe LGCC in the proximal ascending colon discovered after complicated sigmoid diverticulitis in a young woman. Case Description/Methods: A 39-year-old woman with no family history of gastrointestinal malignancy presented with left lower quadrant pain and hematochezia. Computed tomography (CT) demonstrated acute sigmoid diverticulitis with foci of extraluminal gas concerning for microperforation, without abscess. She was treated with intravenous ceftriaxone and metronidazole, then oral ciprofloxacin and metronidazole at discharge. Repeat CT one month later showed near-complete resolution. Two months after diagnosis, colonoscopy demonstrated only mild sigmoid diverticulosis but, unexpectedly, a 2 cm smooth sessile polyp in the proximal ascending colon, resected en bloc by endoscopic mucosal resection. Histopathology revealed well-differentiated invasive adenocarcinoma in tubular adenoma, consistent with LGCC. Mismatch repair (MMR) immunohistochemistry was intact for MLH1, MSH2, MSH6, and PMS2. Staging CT showed no metastases aside from an indeterminate 6 mm right upper lobe nodule. A relook colonoscopy tattooed the polypectomy site for surgical localization, and she was referred to colorectal surgery and genetic counseling. Discussion: This case offers three teaching points. First, complicated diverticulitis below screening age may be a sentinel event for early-onset colorectal cancer (CRC). Second, neoplasia may occur remote from the inflamed area; anchoring on the inflammatory diagnosis risks missing concurrent neoplasia, and complete colonoscopy is essential. Third, LGCC is a rare variant whose natural history is being defined, with reported nodal metastasis in a subset and possible association with sporadic MMR deficiency, though its relationship to Lynch syndrome remains undefined. Early-onset CRC warrants germline evaluation for Lynch syndrome and other hereditary CRC syndromes despite MMR-proficient immunohistochemistry, as MSH6 and PMS2 variants can retain protein expression. AI use disclosure: Generative AI tools assisted with literature review and language editing; no patient-identifiable information was entered, and authors verified content. A B Figure 1. Contrast-enhanced axial CT of the abdomen and pelvis. (A) Initial study demonstrating acute sigmoid diverticulitis with tiny foci of extraluminal gas concerning for microperforation (arrow), without abscess. (B) Axial CT at the matched anatomic level one month later, showing near-complete resolution. A D B C C E Figure 2. Endoscopic and histopathologic findings from the colonoscopy and resection of the proximal ascending colon polyp. (A) Two-centimeter smooth sessile polyp in the proximal ascending colon, identified two months after the index diverticulitis episode. (B) Close-up view of the polyp surface demonstrating mucosal detail. (C) Polypectomy site immediately following en bloc endoscopic mucosal resection, showing the resection bed prior to endoclip placement. (D) Low-power hematoxylin and eosin stain demonstrating the surface tubular adenoma overlying nodular lymphoid aggregates containing invasive carcinoma — the architectural hallmark of lymphoglandular complex-like morphology. (E) Higher-power view of an invasive focus, showing irregular, angulated malignant glands embedded within dense lymphoid stroma.
Type
Poster
Affiliations
Aurora Health Care