Aim: To present a patient with an uncommon primary extramedullary plasmocytoma in the colon. Case report: We report a case of a 64 year old female with wasting syndrome and low-gastrointestinal bleeding. Histology described colon and rectum with plasma cell infiltration in the muscle layer. The immunohistochemistry showed CD45 (+) and lambda (+). Infiltration of bone marrow and other places with a thoraco-abdominal-pelvic scan, blood tests, bone survey and bone marrow biopsy was discarded. Surgical management was performed by laparoscopic low anterior resection with end colostomy. Conclusion: Primary plasmacytoma of colon is a rare clinical entity that is a challenge for the pathologist and surgeon, but early diagnosis contributes to early handling.