B cell malignancies presenting with unusual bone involvement and mimicking multiple myeloma. Study of nine cases.

Nine unusual cases of B cell malignancies presenting with lytic bone lesions on radiography and/or hypercalcemia, and mimicking multiple myeloma are reported in this study. These cases included acute lymphoblastic leukemia (one patient), non-Hodgkin's lymphoma (five patients), chronic lymphocytic leukemia (two patients), and Waldenström's disease (one patient). Quantitative bone biopsy performed in two patients (one with non-Hodgkin's lymphoma and one with Waldenström's disease) demonstrated a dramatic increase in osteoclastic resorption close to tumor cells in both cases, similar to or even more marked than that observed in multiple myeloma. Finally, significant production of bone resorbing activity was found in short-term liquid culture specimens of tumor cells in eight of the nine cases. These observations clearly indicate that in B cell disorders other than multiple myeloma, the malignant B cells can produce significant bone resorbing activity in vitro and result in excessive osteoclastic resorption and lytic bone lesions, frequent hypercalcemia, and an overall disease picture clinically mimicking multiple myeloma.