| Summary: | Primary gastrointestinal T-cell lymphoma is an uncommon entity and primary colon T-cell lymphoma is even rarer. The majority of enteropathy-associated T-cell lymphomas present predominantly as ulcers or strictures in the endoscopic examinations, while primary B-cell lymphomas commonly present as exophytic lesions. Ulcerative colon T-cell lymphoma may mimic Crohn's disease (CD), which is a chronic inflammatory disease of the intestines with ulcer and fistula formations difficult for clinicians to diagnose based on endoscopic observations alone. Like CD, T-cell lymphoma may be characterized by the presence of multiple skipped ulcers distributed from the terminal ileum to the descending colon. Furthermore, it is difficult to diagnose this unusual lymphoma by a single endoscopic biopsy. Typically, the histological composition of T-cell lymphoma is made of medium to large atypical cells located in the base of the ulcer with extension to the muscle layer and the adjacent mucosa. However, it is common that biopsy specimens show only mixed inflammatory changes where the lymphoma cells are hard to be identified. The differential diagnosis of malignant lymphoma must be considered when clinically diagnosed CD is refractory to the medical treatment or when its clinical behavior becomes aggressive. The current study presents a rare case of primary colon T-cell lymphoma in a 56-year-old male with marked recent weight loss, watery diarrhea and bilateral neck lymphadenopathy, who received a laboratory checkup and endoscopic workup for colon biopsy. The initial pathological report was consistent with mucosal inflammation and benign colon ulcers. Interestingly, the blood test showed a prominent eosinophilia. A biopsy of the enlarged neck lymph nodes done approximately 1 month after the colon biopsy unexpectedly showed T-cell lymphoma, which led to a review of the initial colonic biopsy specimens. Additional immunohistochemical stains were used accordingly, which showed positive results for CD3, CD45RO and LCA antibodies confirming the diagnosis of lymphoma. The endoscopic diagnosis of ulcerative colon T-cell lymphoma is frequently confused with inflammatory conditions of the large bowel such as CD, and tuberculosis colitis. Our study aims to emphasize the difficulty in differentiating this ulcerative form of colon T-cell lymphoma from the inflammatory bowel diseases and the importance of its differential diagnosis due to the much more aggressive clinical behavior of the T-cell lymphoma.
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