musculoskeletal and connective tissue disorders
Metastatic Bone Tumors
Diagnosis of Metastatic Bone Tumors
X-ray of the entire bone Whole body radionuclide technecium-99m bone scanning to identify metastases Advanced imaging (CT, MRI, and/or whole body PET-CT scanning for selected purposes) Clinical evaluation and testing to diagnose the primary tumor (if unknown) Often biopsy if the primary tumor is unknown after assessment Metastatic bone tumors are considered in all patients with unexplained bone pain, but particularly in patients who have Known cancer Pain or radiographic abnormalities at more than one site Findings on imaging studies that suggest metastases Prostate cancer is most often blastic, lung cancer is most often lytic, and breast cancer may be blastic or lytic. CT and particularly MRI are highly sensitive for specific metastases. However, if metastases are suspected, a radionuclide whole-body scan, which is not quite as sensitive or specific, is usually done. Bone scan is more sensitive for early and asymptomatic bone metastases than plain x-rays and can be used to scan the entire body. Lesions on the scan are usually presumed to be metastases if the patient has a known primary cancer. Metastases should be suspected in patients who have multiple lesions on bone scan. Although metastases are suspected in patients with known cancer and a single bone lesion, the lesion may not be a metastasis; thus, a needle biopsy of the lesion is often done to confirm the diagnosis of a metastasis. Whole-body PET-CT is now often used for some tumors; it is more specific for bone metastases than is radionuclide bone scan and can identify many extraskeletal metastases. An evaluation to identify an initially unknown primary cancer in a patient with a single or multiple bony lesions includes a comprehensive history and physical examination; CT of the chest, abdomen, and pelvis; mammography in females; and prostate-specific antigen (PSA) measurement in males. Such an approach will identify the primary cancer over 85% of the time. However, bone biopsy, especially fine-needle or core biopsy, is necessary if metastatic tumor is suspected and the primary tumor has not been otherwise diagnosed. Biopsy with use of immunohistologic stains may give clues to the primary tumor type. Sometimes the primary tumor cannot be identified after these tests plus PET-CT and any indicated endoscopy. In patients who present with a fracture, especially older patients, it is important to determine if it is a pathologic fracture due to a cancer. Such a fracture should be suspected if the patient has a known primary cancer. However, the fracture may be the initial manifestation of a cancer elsewhere in the body. The radiographic appearance may be destructive, suggesting a cancer, but may have only subtle abnormalities, for example, such as punctate calcifications that are easily missed may be the only findings suggesting a cancer. Also, although unusual, a bone lesion thought to be the cause of a metastatic fracture may be a fracture through a primary bone tumor such as chondrosarcoma or osteosarcoma. An atypical (as judged by patient age or radiographic appearance) destructive "metastatic" lesion with or without fracture especially with punctate calcifications must be discriminated from the rare primary bone tumor with the help of a musculoskeletal surgical oncologist or musculoskeletal radiologist. 