Background: Lesions characterized by myeloma are lytic lesions surrounded by sclerosis. Diffuse or wide-length sclerotic bone lesions associated with myeloma are infrequent. Case presentation: Two men, 70 and 72 years old, were referred from oncology to hematology for diffuse, large-length sclerotic bone lesions. Their findings were interpreted as having bone metastasis of primary cancer in orthopedics, internal medicine, and oncology due to diffuse sclerotic bone lesions found incidentally during the examinations performed for another reason. The probable causes (prostate, lung, and gastrointestinal cancer) of metastasis were investigated, and they were referred to hematology after a nearly 2-month examination period. Conclusion: The remarkable extensive sclerotic bone lesions may mask the myeloma and may not be considered in the differential diagnosis. However, these cases had the typical clinical findings and laboratory results of MM, except for bone disease. Therefore, we aimed to highlight this issue.

Keywords: Tumor, Metastasis, Multiple myeloma, Sclerotic lesions, Bone, Case report.