Bone or cartilage mass overview

# Overview
Tumors of the bone (also known as "Bone and cartilage tumors") are generally defined as the neoplastic growth of tissue in the bone and cartilage. Abnormal growths found in the bone can be benign or malignant. Bone and cartilage tumors may be classified according to the WHO histological classification system into 5 sub-types: cartilage tumors, osteogenic tumors, fibrohistiocytic tumors, notochordal tumors, hematopoietic tumors, and miscellaneous tumors. In addition, bone and cartilage tumors may be sub-classified according to tumor location into 4 subtypes: diaphysis, metaphysis, epiphysis, and ungrouped/others. "Primary bone tumors", which originate in bone or from bone-derived cells and tissues, and "secondary tumors" which originate in other sites and metastasize to the skeleton, is another nomenclature to classify bone tumors. Carcinomas of the prostate, breasts, lungs, thyroid, and kidneys are the carcinomas that most commonly metastasize to bone. Secondary malignant bone tumors are more common than primary bone cancers. Bone and cartilage tumors are uncommon, they represent 0.2% of all neoplasms in general population. The prevalence of bone and cartilage tumors is approximately 0.9 per 100,000 individuals. Bone and cartilage tumors have a bimodal age distribution. These tumors are more frequent in children and adolescents, and older adults. Bone and cartilage tumors are slightly more common among individuals of Caucasian race. The most common symptom of bone tumors is pain, which will gradually increase over time. The pain increases with the growth of the tumor. Additional symptoms may include fatigue, fever, weight loss, anemia, and/or sudden bone fractures. In some cases, bone tumors may be asymptomatic. Bone tumors may weaken the structure of the bone, causing pathologic fractures.

# Classification
Bone and cartilage tumors may be classified according to the WHO histological classification system into benign and malignant tumors, and categorized into 5 sub-types: cartilage tumors, osteogenic tumors, fibrohistiocytic tumors, notochordal tumors, hematopoietic tumors, and miscellaneous tumors. In addition, bone and cartilage tumors may be sub-classified according to tumor location into 4 subtypes: diaphysis,  metaphysis,  epiphysis, and ungrouped/others. "Primary bone tumors", which originate in bone or from bone-derived cells and tissues, and "secondary tumors" which originate in other sites and metastasize to the skeleton, is another nomenclature to classify bone tumors. Carcinomas of the prostate, breasts, lungs, thyroid, and kidneys are the carcinomas that most commonly metastasize to bone. Secondary malignant bone tumors are more common than primary bone cancers. Common benign bone tumors, include: osteoma, osteoid osteoma, osteochondroma, aneurysmal bone cyst, and fibrous dysplasia. Common malignant bone tumors, include: osteosarcoma, Ewing's sarcoma, and chondrosarcoma. Secondary bone tumors include metastatic tumors which have spread from other organs (usually, adenocarcinomas). In general, metastatic tumors frequently involve the axial skeleton and the appendicular skeleton. Common secondary bone tumors, include: breast cancer, lung cancer, and prostate cancer.

# Causes
Bone and cartilage tumors may be caused by precursor lesions, such as radiation injury, chronic osteomyelitis, and some genetically determined syndromes (McCune-Albright syndrome, Ollier disease, Maffucci syndrome, and Beckwith-Wiedemann syndrome).

# Differential Diagnosis
Bone and cartilage tumors may be differentiated according to clinical features, laboratory findings, imaging features, histological features, and genetic studies, from other diseases that cause limited range of motion, bone pain, local swelling, and limb deformity. Common differential diagnosis includes: osteoma, osteosarcoma, chondroma, chondrosarcoma, Ewing sarcoma, giant cell tumor, and metastases.

# Epidemiology and Demographics
Bone and cartilage tumors are uncommon, they represent 0.2% of all neoplasms in general population. The prevalence of bone and cartilage tumors is approximately 0.9 per 100,000 individuals. Bone and cartilage tumors have a bimodal age distribution. These tumors are more frequent in children and adolescents, and older adults.  The average age at diagnosis is between 10-25 years old and 60-75 years old. Males are more commonly affected than females, with a 1.5:1 ratio. Bone and cartilage tumors are slightly more common among individuals of Caucasian race.

# Screening
According to the the National Cancer Institute (NCI) there is insufficient evidence to recommend routine screening for bone or cartilage tumors.

# Diagnosis

## Evaluation of Bone or Cartilage Mass
The evaluation of bone or cartilage mass will depend on detailed medical history, age, and morphology of the lesion.

## Staging
According to the Enneking system there are 6 stages of benign and malignant bone and cartilage tumors based on the grade, anatomic site, and metastasis.

## History and Symptoms
Bone and cartilage tumors are generally asymptomatic. The majority of patients may develop non-specific symptoms, such as: dull localized bone pain (related with locally aggressive tumors), adjacent muscle soreness, local swelling or mass, progressive pain that is not relieved with rest, night pain, and recent weight loss. Obtaining the detailed history is an important aspect of making a diagnosis of bone and cartilage tumors, specific areas of focus when obtaining the history, are personal history of cancer, and family history of bone tumors.

## Physical Examination
Physical examination findings of bone or cartilage masses will depend on the location of the tumor. Common physical examination findings include skeletal deformity, swelling, increased skin temperature, increased sweating, and tenderness.

## Laboratory Studies
Laboratory findings consistent with the diagnosis of bone and cartilage tumors, may include:  elevated LDH,  elevated alkaline phosphatase (related with prognosis), and elevated aspartate aminotransferase (AST).

## Imaging
Conventional radiography is the method of choice for the diagnosis of bone and cartilage tumors. The evaluation of bone and cartilage tumors will depend on 7 characteristics: periosteal reaction, opacity and mineralization, location, size, margins, cortical involvement, and soft-tissue component.

## Biopsy
Bone biopsy findings associated with bone and cartilage tumors will depend on tumor histology, common findings include: anastomosing bony trabeculae, calcifications surrounded by cells nests, and increased/decreased osteoblasts and osteoclasts.

## Other Diagnostic Studies
Bone scintigraphy may be helpful in the diagnosis of bone and cartilage tumors. Radioisotopes play an important role in the differential diagnosis between benign and malignant bone lesions.

# Acknowledgements
The content on this page was first contributed by: Editor-In-Chief: C. Michael Gibson, M.S., M.D.