BONE AND JOINT TUMORS

BONE AND JOINT TUMORS

The classification of bone tumors, as well as positive diagnosis?, is difficult. The origin of these tumors may be different, from the bone skeleton, from the possibility of appearance in connective tissues, whose plasticity is well known. Thus, tumors may originate from the connective tissue proper, from blood vessels, cartilage? and various cell types, such as bone cells, osteoclasts, osteoblasts or their precursors. The possibilities of embryogenic transformation are added, including myxomatous, cartilaginous and bone transformation.

A classification of bone tissue and cartilaginous tissue tumors depending on histological structure recognizes, in spite of al inherent difficulties, the neoplasms specific for these tissues, as well as the possibility of cancerization of other structures, such as blood vessels, connective tissue or periarticular tissues [10,15].

The anatomohistological classification includes:

• – osteoma;
• – osteoid osteoma;
• – osteosarcoma;
• – juxtacortical osteosarcoma;
• – fibrosarcoma;
• – liposarcoma;
• – osteoliposarcoma;
• – chondroma;
• – osteochondroma;
• – chondrosarcoma;
• – multilobular bone tumor?;
• – bone marrow? tumors: myeloma?;
• – vascular tumors; hemangioma; hemangiosarcoma;
• – mixed bone tumors;
• – metastatic bone tumors;
• – tumor-like bone lesions: solitary bone cyst; aneurysmal bone cysts;
• – articular and adnexal structure tumors: synovial sarcoma?; fibroxanthoma; malignant? giant cell tumor of the connective tissue.

Histological Classification of Bone and Joint Tumors of Domestic Animals (Slayter et al. 1994)

1. BENIGN? TUMORS
   1. Osteoma
   2. Ossifying fibroma
   3. Myxoma of the jaw
   4. Osteochondroma
   5. Feline osteochondromatosis
   6. Chondroma
   7. Hemangioma
2. MALIGNANT TUMORS
   1. Central
      1. Osteosarcoma
         1. poorly differentiated
         2. osteoblastic
            • – nonproductive
            • – productive
         3. chondroblastic
         4. fibroblastic
         5. telangiectatic
         6. giant cell type
      2. Chondrosarcoma
      3. Fibrosarcoma
      4. Hemangiosarcoma
      5. Giant cell tumor of bone
      6. Multilobular tumor of bone
   2. Peripheral
      1. Periosteal chondrosarcoma
      2. Periosteal fibrosarcoma
      3. Maxillary fibrosarcoma (dogs)
      4. Periosteal osteosarcoma
      5. Parosteal osteosarcoma
   3. Joint tumors
      1. Synovial sarcoma
   4. Miscellaneous tumors
      1. Liposarcoma
      2. Malignant mesenchymoma
      3. Others
   5. Tumors of bone marrow
      1. Myeloma
      2. Malignant lymphoma?
3. TUMOR-LIKE LESIONS
   1. Fibrous dysplasia
   2. Solitary bone cyst
   3. Juxtacortical bone cyst
   4. Epidermoid cyst of the phalanx
   5. Myositis ossificans
   6. Villonodular synovitis

Histological Differential Diagnosis? [11]

• Osteoid osteoma
• Aneurysmal bone cyst
• Giant cell tumor of bone
• Osteoma with osteoblastoma-like features
• Osteoblastoma-like osteosarcoma

Radiological Differential Diagnosis [5]

• Osteoid osteoma
• Aneurysmal bone cyst
• Infection? (Brodie abscess)
• Osteosarcoma
• Metastasis?