Primary isolated rectal diffuse large B-cell lymphoma with recto-vaginal fistula: a case report and review of the literature

Primary rectal lymphoma is a rare malignancy, accounting for only 0.2–0.6% of all colorectal tumors, with diffuse large B-cell lymphoma (DLBCL) being the most common subtype. The clinical presentation is often non-specific, leading to delayed diagnosis. Due to its rarity, the optimal treatment approach remains controversial. We present a unique case of a 17-year-old female diagnosed with primary isolated rectal DLBCL complicated by a rectovaginal fistula. A 17-year-old Ethiopian nulligravida patient presented with a rectal mass protruding through the vagina, accompanied by foul-smelling fecal discharge. She had experienced amenorrhea for seven months, along with intermittent lower abdominal pain, tenesmus, and blood on stool. Examination revealed a fragile, cauliflower-like rectal mass extending into the vaginal wall, forming a rectovaginal fistula. Imaging and colonoscopy confirmed a locally advanced rectal mass, and histopathology established a diagnosis of high-grade non-Hodgkin lymphoma, consistent with DLBCL. The patient underwent a sigmoid loop colostomy followed by six cycles of chemotherapy with vincristine, cyclophosphamide, methotrexate, and prednisone. She demonstrated significant improvement, with complete tumor regression. Primary isolated rectal DLBCL is an exceptionally rare entity, particularly in young patients, with limited data guiding its management. Distinguishing rectal lymphoma from adenocarcinoma is challenging due to overlapping clinical and radiological features, making histopathological confirmation essential. Current treatment strategies involve chemotherapy as the mainstay, with surgery reserved for complications, such as obstruction, perforation, or fistula formation. The CHOP regimen, sometimes augmented with rituximab, has shown favorable outcomes. The role of surgical resection in rectal lymphoma remains debated, with emerging evidence suggesting that chemotherapy alone may be sufficient in many cases. This case underscores the importance of considering rectal lymphoma in young patients presenting with rectal masses and atypical symptoms. Early recognition and histopathological diagnosis are crucial for guiding appropriate therapy. Larger studies are needed to establish standardized treatment protocols and optimize patient outcomes.