Given the macroscopic appearance, a hyperplastic polyposis syndrome was suspected. However, histological examination of biopsy specimens did not confirm the macroscopic diagnosis. A monomorphic lymphoid proliferation with a diffuse architectural effacement in all tissue samples (figures 2A and 2B). Immunostaining revealed mantle cell lymphoma (MCL). Subsequent staging with an FDG-PET/CT scan showed ileocecal and rectal mucosal thickening, mesenterial and retroperitoneal lymphadenopathy, as well as pulmonary nodules, all minimally FDG avid. A CT-guided biopsy of a retroperitoneal lymph node confirmed the diagnosis of MCL. A bone marrow biopsy was positive for MCL (20% infiltration). The MCL International Prognostic Index (MIPI) score was calculated to be 5.5 (low risk).
The patient was treated with alternating cycles of R-CHOP and R-DHAP given every 21 days for a total of six cycles after which, a complete remission was documented by PET/CT scan. Consolidative BEAM chemotherapy supported by an autologous stem cell transplant was given. Subsequently, rituximab maintenance therapy every two months was started. The abdominal complaints disappeared; the stool became normal. A repeat colonoscopy 12 months later showed an entirely normal colon. MCL comprises about 7% of all non-Hodgkin lymphomas in Western Europe. Involvement of the gastrointestinal tract is reported in 5-20% of all cases. Primary gastrointestinal lymphoma comprises possibly 1-4% of all gastrointestinal malignancies.1 Localisation in the colon is exceptional. Most patients with multiple lymphomatous polyposis are already known to have MCL.2 The most common clinical presentation is abdominal pain and weight loss.3
MCL most commonly presents in the proximal colon as a mass with ulceration which can lead to intestinal obstruction or intussusception, requiring surgery.4 Endoscopic features can be heterogeneous, encompassing ulcers, erosions, and polyps, and occasionally presenting as multiple lymphomatous polyposis. The present case shows a MCL diffusely in the colon mimicking a hyperplastic polyposis syndrome.