X-ray of a giant cell<unk>  in the head of the 4th metacarpal of the left hand. An arm<unk> <unk> s are traditionally classified as noncancerous (benign) or cancerous (malignant). Several features of<unk> s and soft tissue<unk> s overlap. Their classification was revised by the World Health Organization (WHO) in 2020. This newer classification categorises<unk> s into cartilage<unk> s, osteogenic<unk> s, fibrogenic<unk> s, vascular<unk> s of<unk> , osteoclastic giant cell-rich<unk> s, notochordal<unk> s, other mesenchymal<unk> s of<unk> , and hematopoietic neoplasms of<unk> .<unk> s may be classified as "primary<unk> s", which originate in<unk>  or from<unk> -derived cells and tissues, and "secondary<unk> s" which originate in other sites and spread (metastasize) to the skeleton. Carcinomas of the prostate, breasts, lungs, thyroid, and kidneys are the carcinomas that most commonly metastasize to<unk> . Secondary malignant<unk> s are estimated to be 50 to 100 times as common as primary<unk>  cancers. Primary<unk> s Primary<unk> s of<unk>  can be divided into benign<unk> s and cancers. Common benign<unk> s may be neoplastic, developmental, traumatic, infectious, or inflammatory in etiology. Some benign<unk> s are not true neoplasms, but rather, represent hamartomas, namely the osteochondroma. The most common locations for many primary<unk> s, both benign and malignant include the distal femur and proximal tibia (around the knee joint). Examples of benign<unk> s include osteoma, osteoid osteoma, osteochondroma, osteoblastoma, enchondroma, giant cell<unk>  of<unk>  and aneurysmal<unk>  cyst. Malignant primary<unk> s include osteosarcoma, chondrosarcoma, Ewing's sarcoma, fibrosarcoma, and other types. While malignant fibrous histiocytoma (MFH) - now generally called "pleomorphic undifferentiated sarcoma" - primary in<unk>  is known to occur occasionally, current paradigms tend to consider MFH a wastebasket diagnosis, and the current trend is toward using specialized studies (i.e. genetic and immunohistochemical tests) to classify these undifferentiated<unk> s into other<unk>  classes. Multiple myeloma is a hematologic cancer, originating in the<unk>  marrow, which also frequently presents as one or more<unk>  lesions. Germ cell<unk> s, including teratoma, often present and originate in the midline of the sacrum, coccyx, or both. These sacrococcygeal teratomas are often relatively amenable to treatment. Secondary<unk> s Secondary<unk> s are metastatic lesions which have spread from other organs, most commonly carcinomas of the breast, lung, and prostate. Rarely, primary<unk>  malignancies such as osteosarcoma may also spread to other<unk> s. Reliable and valid statistics on the incidence, prevalence, and mortality of malignant<unk> rs are difficult to come by, particularly in older adults (those over 75 years of age) - because carcinomas that are widely metastatic to<unk>  are rarely ever curable. Biopsies to determine the origin of the<unk> r in cases like this are rarely done.
Bone tumor
Bone metastasis
Osteomyelitis
Osteoma
Endocrine bone disease
Spinal fracture
Osteopetrosis
Vertebral osteomyelitis