We describe a solitary extramedullary plasmacytoma of the breast in a 37-ye
ar-old woman. No other involvement was detected in the bone marrow or in an
y other site during a 15-month follow-up period. Extramedullary plasmacytom
as of the breast are extremely rare, especially those that are not associat
ed with multiple myeloma. We review the histologic features of the previous
ly reported cases with an emphasis on differential diagnosis and the diffic
ulties encountered in arriving at the correct diagnosis in frozen sections.