Suspicious bone lesions spotted in patients with one known malignancy should not be assumed to represent metastases from the primary malignancy, as some of these lesions will be benign or due to a previously unknown second malignancy, according to a study published in the December issue of the American Journal of Roentgenology.

The study demonstrated that in a group of nearly 500 patients at a tertiary cancer center, 24 percent of patients had bone lesions that were not metastases from the known primary malignancy, and assuming this is the case could result in mismanagement of a different cancer in some patients, according to Barbara Raphael, MD, of Memorial Sloan-Kettering Cancer Center in New York City, and colleagues.

“Moreover, assuming that a benign lesion actually represents a metastasis could result in inappropriate changes in patient management,” added the authors.

Records of 482 consecutive patients with only one known primary malignancy and who underwent biopsy of a suspicious bone lesion were retrospectively reviewed by the authors. Patients with non-melanoma skin cancer were excluded.

While two-thirds of the lesions were metastases of the known malignancy, 21 percent of patients had benign bone biopsy results, reported the authors. Another 3 percent of bone lesions were due to a second malignancy. The remaining biopsies were nondiagnostic or indeterminate.

Second malignancies included osteosarcoma, soft-tissue sarcoma, lymphoma, plasma cell malignancy, lung cancer, thyroid cancer, renal cancer, and chondrosarcoma, as well as a carcinoma of an unknown primary, according to Raphael and colleagues.

The authors added that the number of suspicious bone lesions was not predictive of the presence of a second malignancy.

“Bone biopsy is recommended in the management of patients with one known cancer and a suspicious bone lesion only if the presence of a second malignancy would alter clinical management,” wrote Raphael and colleagues. They also recommended biopsies in situations where:

• The imaging features of the bone lesion are not those usually encountered in the known primary cancer type;
• Bone metastases rarely occur or would be uncommon as the sole site of metastasis in the primary cancer type;
• The suspicious bone lesion is in a previously irradiated field;
• There has been an unusually long time interval since initial diagnosis that is not typical for metastasis from the primary tumor; and
• The suspicious bone lesion is located in an unusual skeletal site for a metastasis, such as the carpus, fibula, or phalanx.