Strategy for the treatment and follow-up of sinonasal solitary extramedullary plasmacytoma: a case series

BACKGROUND Extramedullary plasmacytoma is a rare neoplasm characterized by monoclonal proliferation of plasma cells outside bone marrow. It accounts for 4% of all non-epithelial sinonasal tumors. According to the literature, radiotherapy is the standard therapy for extramedullary plasmacytoma. However, the conversion rate of extramedullary plasmacytoma to multiple myeloma is reported to be between 11 and 33% over 10 years. The highest risk of conversion is reported during the first 2 years after diagnosis, but conversion has been noted up to 15 years after diagnosis. Once conversion to multiple myeloma is complete, less than 10% of patients will survive 10 years. CASE PRESENTATION We present three cases of sinonasal extramedullary plasmacytoma who underwent radiotherapy: a 61-year-old white man, a 60-year-old white man, and a 37-year-old white woman. We found long-term survival with stable disease in all three cases. CONCLUSIONS The management of solitary extramedullary plasmacytomas of the sinonasal tract is not well established yet. However, the possibility of recurrence and progression to multiple myeloma requires a thorough follow-up protocol. Due to the absence of a standardized protocol for these tumors, we tried to design a tailored long-term follow-up scheme.