Colorectal lymphomas of primary origin are rare neoplasms accounting for 3% of all lymphomas involving the gastrointestinal (GI) tract, and of that 3%, 0.1-0.5% involve the colorectal region. Among the types of non-Hodgkin's lymphomas involving the GI tract, diffuse large B-cell lymphoma (DLBCL) is the most common type. While extranodal involvement of DLBCL in the GI is common, DLBCL of the colon with Epstein-Barr virus positivity is a rare entity with only a few cases reported in the literature. Here, we present a rare case of a 53-year-old female with human immunodeficiency virus (HIV) who presented with generalized abdominal pain, weight loss, night sweats, and fevers. A computed tomography scan of the abdomen and pelvis showed a mass on the right side of the colon with associated retroperitoneal and right inguinal lymphadenopathy. She later underwent a colonoscopy with a biopsy. Histopathology showed DLBCL of the ascending colon and chemotherapy was initiated.

Multiple myeloma (Kahler disease) is a monoclonal plasma cell immunoproliferative neoplasm originating within the bone marrow that involves the production of monoclonal immunoglobulins, mostly IgG and IgA. Extramedullary plasmacytoma (EMP) is a subset of plasma cell neoplasms that can develop in patients at the time of diagnosis with multiple myeloma, or relapse of the disease. Symptoms related to plasmacytomas depend on the primary location. Here in, we present a rare case of extramedullary plasmacytoma involving the portacaval space in an 83-year-old African American female with relapsed multiple myeloma. She was treated successfully with radiation therapy with complete resolution of the mass. In this case report, we aim to discuss the clinical features along with diagnostic methods and treatment for extramedullary plasmacytomas with emphasis on utilizing a multidisciplinary approach in managing these rare cases.