A bone biopsy is mandatory in the optimal management of bone lesions in patients with a long-term history of malignancy of the breast.

Bone lesions, present in two women with primary breast cancer treated more than 5 years ago, were investigated thoroughly by biochemical markers and imaging techniques. The definite diagnosis was established by bone biopsy, which revealed two totally unrelated disorders that altered the management and prognosis for these two patients. One patient had Paget's disease, and the other had metastatic hepatocellular carcinoma.