Background: Cutaneous plasmacytoma is a very rare manifestation of extramedullary plasmacytoma, with only 32 cases having been reported so far in the last 60 years. Extramedullary plasmacytoma is a plasma cell tumor that involves soft tissues, without any signs of systemic spread of multiple myeloma or bone marrow involvement. The cutaneous lesions usually range in diameter from 1 to 5 cm and can be treated with radiotherapy or surgical excision.

Conclusions: We present a case of a giant cutaneous plasmacytoma of the sacrococcygeal region with a diameter of 12 cm that was treated with surgical excision.