Multiple lymphomatous polyposis is an uncommon type of primary non-Hodgkin's gastrointestinal B cell lymphoma. It is considered to represent mantle cell lymphoma of the gastrointestinal tract mainly. However, rarely some cases of multiple lymphomatous polyposis belong to follicular lymphoma, small lymphocytic lymphoma, diffuse large cell lymphoma, or mucosa-associated lymphoid tissue lymphomas. Recently, WHO 2008 classification established a new diagnostic category of B cell lymphoma, unclassifiable, with features intermediate between DLBCL and BL (DLBCL/BL). To the best of our knowledge, this subcategory of lymphoma presenting as lymphomatous polyposis has never been described. We herein describe a case of lymphomatous polyposis involving entire gastrointestinal tract, which turned out as DLBCL/BL on immunohistochemistry and molecular analysis. The patient was treated with hyper-CVAD chemotherapy regimen, resulting in a complete response.