PURPOSE Staging of cancer is essential to formulate appropriate treatment plans and to help predict prognosis. A solitary region of increased radionuclide uptake ("hot spot") on a bone scan may represent a metastasis or a masquerading lesion. Biopsy may be required to determine its histologic nature, but localization of the site may be difficult because bone scans provide poor spatial resolution. METHODS In two patients with breast carcinoma, radioactive technetium was administered intravenously and a gamma probe was used preoperatively and intraoperatively to identify the site of cranial bone involvement. RESULTS The lesions were resected; one was a benign fibro-osseous lesion and one was a metastatic breast adenocarcinoma. CONCLUSIONS A gamma probe may be helpful in localizing the site of radioactive uptake identified by bone scan.