Primary Colorectal Lymphoma Presenting as a Perisigmoid Abscess: A Report of a Rare Case.

Primary colon lymphoma is an extremely rare condition that can affect men more frequently. It typically presents with symptoms such as abdominal pain, weight loss, and a change in bowel habits. In this case, we report on a 78-year-old female patient who visited the Emergency Department due to pain in the lower left quadrant of the abdomen. The initial evaluation included a computed tomography scan, which revealed concentric thickening of the sigmoid colon, associated with a mesenteric border abscess, as well as lymphadenopathies in the retroperitoneum and mesentery. These radiological findings raised suspicion of perforated diverticulitis, as well as lymphoma, as differential diagnoses. Antibiotic treatment was initiated to control the abscess, and a colonoscopy with biopsy was subsequently performed. Histopathological examination confirmed the diagnosis of B-cell non-Hodgkin lymphoma (NHL), classified as clinical stage IV due to the observed lymphatic dissemination. Although chemotherapy was offered as a potential treatment, the patient declined it for personal reasons. Primary colorectal lymphoma is a sporadic entity, and to the best of our knowledge, there are very few articles reporting it in association with a mesenteric abscess. This case highlights the importance of considering rare diagnoses in patients with gastrointestinal symptoms. Furthermore, it underscores the need for a multidisciplinary approach to managing such conditions, involving collaboration among radiologists, gastroenterologists, hematologists, oncologists, and pathologists to ensure accurate diagnosis and appropriate treatment.