Extramedullary Plasmacytoma of the Cecum: A Rare Cause of Iron Deficiency Anemia

Abstract

Introduction: Plasmacytomas are solid myelomatous tumors composed of atypical plasma cells, which can be formed within bone or less commonly within soft tissue. Plasmacytomas are commonly associated with multiple myeloma (MM), however they may manifest outside the context of MM as solitary plasmacytomas. Extramedullary plasmacytomas are most commonly found in the aerodigestive tract, however they may present anywhere in the body. Here we present a rare case of a woman with iron deficiency anemia secondary to a cecal plasmacytoma not associated with MM. Case Report: A 73-year-old woman presented with iron deficiency anemia. Two years prior she had been diagnosed with a solitary extramedullary plasmacytoma in her right posterior mediastinum with intraspinal extension to T3. She underwent curative T2-T5 laminectomy and radiotherapy. Her disease was considered in remission at the time of presentation. After treatment of her profound iron deficiency anemia with intravenous iron, a single contrast barium enema was performed. It showed a large polypoid lesion in the lateral proximal ascending colon below the level of the ileocecal valve. These findings were indicative of colonic neoplasm and she was referred for colonoscopy. Colonoscopy confirmed the presence of a 4 cm fungating tumor at this location. This tumor was not amenable to endoscopic removal. Biopsies were taken for pathology which demonstrated plasmacytic infiltrate with frequent mitotic activity consistent with extramedullary plasmacytomas. Her β2 microglobulin level was elevated (282.5 nmol/L). She was referred back to oncology services where she was treated with concurrent prednisone and radiotherapy - 45 gray in 25 fractions. Discussion: Colonic extramedullary plasmacytomas are exceedingly rare with fewer than 25 cases reported in the literature. Any area of the gastrointestinal tract may be involved; however the most common site of involvement is the sigmoid colon. The most common presenting symptom of colonic plasmacytoma is abdominal pain; other symptoms have also been reported including overt bleeding, large bowel obstruction, and intussusception. We report a rare diagnosis of colonic extramedullary plasmacytoma from a history of iron deficiency anemia without presentation of the aforementioned symptoms. Treatment of plasmacytomas of the colon most commonly involve surgical resection. Radiotherapy and chemotherapy have only played a modest role in treatment. In our case the patient was felt to be a poor surgical candidate, and successful radiotherapy was performed.