Lymphoglandular Complex-Like Colorectal Carcinoma Arising in Tubular Adenoma: A Case Report

Lymphoglandular complex-like colorectal carcinoma (LGCC) is characterized by invasive tumors confined entirely by lymphoid stroma and is very rare. Histologically, it can closely mimic adenomatous polyps involving lymphoglandular complexes (LGCs) or pseudoinvasion/misplacement of adenomatous epithelium. Here, we report a 57-year-old patient who underwent routine surveillance colonoscopy and was found to have a 30 mm sessile polyp in the ascending colon. The polyp was removed by endoscopic mucosal resection. Initial histologic sections show fragments of tubular adenoma. Due to the large size of the polyp, additional levels were ordered. At the second level of the largest fragment, a small focus of lymphoid aggregate is seen beneath the muscularis mucosa, and there is a small focus of tumor glands (< 1 mm) within this lymphoid aggregate. These glands are completely surrounded by the lymphoid tissue and show an infiltrative pattern. There is no interposed lamina propria. The glands exhibit haphazard distribution, gland angulation with luminal debris, and scattered single cells. The tumor cells show high-grade cytologic atypia. CDX2 immunostain highlighted the tumor glands and single cells, supporting the diagnosis of LGCC. Our case shows that LGCC can be diagnostically challenging. Awareness of its morphologic features can help to avoid diagnostic pitfalls.