Minute primary extramedullary plasmacytomas of the large intestine

An 84-year-old woman underwent a follow-up colonoscopy 4 years after undergoing endoscopic mucosal resection (EMR) for colonic adenoma. Two small polyps were found in the cecum and the rectum ([ Fig. 1 a, b ]) and EMR was performed. Fig. 1 Endoscopic appearance of primary extramedullary plasmacytomas. a In the cecum, the slightly reddish sessile polyp with a normal surface was suggestive of a submucosal tumor. b In the rectum, the mucosal surface of the tumor was different from the surrounding normal mucosa, suggesting an epithelial tumor. Histologically, both resected specimens showed a dense infiltration of plasma cells ([ Fig. 2 a, b ]). Fig. 2 Low-power view of primary extramedullary plasmacytomas: a cecal; b rectal. They were considered to be monoclonal neoplastic cells because they were immunohistochemically positive for kappa light chains but negative for lambda light chains ([ Fig. 3 a, b ]). Fig. 3 Immunohistochemical staining for primary extramedullary plasmacytomas: a kappa light chains; b lambda light chains. A subsequent skeletal survey and bone marrow aspirate biopsy were normal. No monoclonal paraprotein was identified in the serum or urine, and there was no hypercalcemia or renal failure. Upper gastrointestinal endoscopy showed atrophic gastritis only. Dynamic computed tomography showed no lesion associated with the plasmacytoma. On the basis of these results, a diagnosis of primary extramedullary plasmacytomas (PEMPs) of the cecum and rectum was made. The diagnosis of PEMP requires demonstration of a monoclonal plasma cell infiltration without evidence of multiple myeloma [ 1 ] [ 2 ]. Approximately 10 % of PEMPs are found in the gastrointestinal tract [ 3 ] [ 4 ]. PEMP of the large intestine is extremely rare, and to the best of our knowledge, only 13 previous cases of PEMP of the large intestine have been reported in the English literature. All of these previous cases were symptomatic, advanced, single tumors, which underwent surgical treatment, except for one case which was resected using EMR [ 5 ]. Tumors in these cases have no special endoscopic appearance, and only one endoscopic image has been published [ 5 ]. In our case, we described two minute PEMPs (cecum = 4 mm in diameter; rectum = 2 mm in diameter) without symptoms in the large intestine with clear endoscopic images. To our knowledge, there are no similar previous reports. In conclusion, our case is very important for the understanding of the early morphology of PEMP in the large intestine.