Extramedullary plasmacytoma of the colon manifesting with intussusception

The WHO categorises plasma cell tumours into two primary types: multiple myeloma and plasmacytoma. Plasmacytoma is further classified into solitary extramedullary plasmacytoma (EMP) and solitary plasmacytoma of bone. The upper respiratory tract and nasopharynx are the sites most commonly affected by EMP. Gastrointestinal tract involvement occurs in approximately 10% of EMP cases, while colonic involvement—particularly when associated with intussusception—is exceedingly rare. We present the case of a middle-aged man in his 40s who reported haematochezia, fatigue and weight loss over a 6-month period, without fever or bone pain. Physical examination revealed pallor. Endoscopic evaluation demonstrated a polypoidal mass at the hepatic flexure of the colon. An initial biopsy suggested a neuroendocrine tumour. Based on this provisional diagnosis, a D3 right extended hemicolectomy was performed. However, subsequent histopathological analysis unexpectedly revealed plasmacytoid cells consistent with EMP.