Bone Tumor Bone tumors develop when cells within a bone divide uncontrollably, forming a lump or mass of abnormal tissue.Most bone tumors are benign (not cancerous). Benign tumors are usually not life-threatening and, in most cases, will not spread to other parts of the body. Depending upon the type of tumor, treatment options are wide-ranging—from simple observation to surgery to remove the tumor.Some bone tumors are malignant (cancerous). Malignant bone tumors can metastasize—or cause cancer cells to spread throughout the body. In almost all cases, treatment for malignant tumors involves a combination of chemotherapy, radiation, and surgery.