An extramedullary plasmacytoma involving the gastrointestinal tract is extremely rare. We report an appendiceal extramedullary plasmacytoma in a 35-year-old man who presented to the emergency department because of upper abdominal pain. Computed tomography (CT) imaging revealed an incidental mass (3.7 × 1.9 × 1.6 cm) at the tip of the appendix. Microscopically, the appendix, periappendiceal soft tissue, and nearby lymph nodes were diffusely infiltrated by plasma cells that were kappa light chain restricted. Subsequent workup included an unremarkable bone marrow biopsy, as well as urine and serum electrophoresis. A diagnosis of kappa-restricted solitary extramedullary plasmacytoma was made. To our knowledge, this is the first case reported of an appendiceal extramedullary plasmacytoma in the medical literature.

Primary bone marrow diffuse large B-cell lymphoma is an exceedingly rare form of non-Hodgkin lymphoma. It may demonstrate a leukemic presentation, and a proportion of cases have CD5 expression. The prognostic implications of this CD5-positivity remain unknown. Here, we present a 78-year-old man who presented with circulating peripheral blood lymphoma cells and a hypercellular marrow involved by diffuse large B-cell lymphoma, germinal center B-cell subtype. The patient responded favorably to six cycles of etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab (EPOCH-R) and intrathecal methotrexate. He unfortunately relapsed in several enlarged inguinal lymph nodes and succumbed to the lymphoma approximately one year after diagnosis, demonstrating the particularly aggressive clinical course of his disease.