Solitary Plasmacytoma of the Humerus

A 43-year-old man presented with pain in right arm since one year. a radiograph of the right arm showed an extensive osteolytic lesion involving the diaphysis of the humerus (figure 1). a biopsy and nailing was done. histopathological examination showed sheets of plasma cells with few immature forms (figure 2). on immunohistochemistry, the tumor cells were cd138 positive with lambda light chain restriction, indicative of plasmacytoma. his hematology and serum chemistries were normal. his quantitative serum immunoglobulins and free kappa lambda were normal. skeletal survey and bone marrow were normal. he received radiation 40 gy to the humerus and is currently on follow up.