© 2005 Foundation for Promotion of Cancer Research
Case Report |
CD56-positive Small Round Cell Tumor: Osseous Plasmacytoma Manifested in Osteolytic Tumors of the Iliac Bone and Femora
1 Hematology, 2 Orthopedics and 3 Pathology Divisions, National Cancer Center Hospital, Tokyo, Japan
For reprints and all correspondence: Takashi Watanabe, Hematology Division, National Cancer Center Hospital 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. E-mail: tkouno{at}ncc.go.jp
Received April 29, 2004; accepted September 6, 2004
Monoclonal gammopathy of undetermined significance does not overexpress cluster of differentiation (CD) 56, but plasma cell myeloma frequently overexpressed it. However, plasma cell leukemia and extramedullary plasmacytoma usually down-regulate CD56 expression. Plasmacytoma, especially ‘solitary plasmacytoma of bone’, is difficult to diagnose as plasma cell neoplasm, because it occasionally appears similar to other bone tumors, both clinically and pathologically, and is rarely accompanied by monoclonal protein in the serum or urine. The present case was a patient with an osteolytic ‘small round cell tumor’ of the iliac bone, which also invaded the femora. An immunohistopathological finding of CD56 expression played a key role in making a diagnosis. The definitive diagnosis of plasmacytoma was made based on the electron microscopic findings. The plasma cells which infiltrated her sternum showed the same restriction to kappa light chain expression in their cytoplasms as that of the iliac bone tumor cells, but did not express CD56. Locally infiltrating osteolytic bone tumors should be examined for surface immunoglobulin light chains as well as CD56 expression when plasmacytoma is suspected.
Key Words: CD56 • osseous plasmacytoma • osteolytic bone tumor • plasmacytoma • SBP