Osteosarcoma is a malignant tumor that is characterized by the direct formation of bone or osteoid tissue by the tumor cells. The World Health Organization's histologic classification  of bone tumors separates the osteosarcomas into central (medullary) and surface (peripheral) [2,3] tumors and recognizes a number of subtypes within each group.
Patients with unresectable extrahepatic bile duct cancer have cancer that cannot be completely removed by the surgeon. These patients represent the majority of cases of bile duct cancer. Often a proximal bile duct cancer invades directly into the adjacent liver or into the hepatic artery or portal vein. Portal hypertension may result. Spread to distant parts of the body is uncommon, though transperitoneal and hematogenous hepatic metastases do occur with bile duct cancers of all sites. Invasion...
The most common pathologic subtype is conventional central osteosarcoma, which is characterized by areas of necrosis, atypical mitoses, and malignant osteoid tissue and/or cartilage. The other subtypes are much less common, each occurring at a frequency of less than 5%. Telangiectatic osteosarcoma may be confused radiographically with an aneurysmal bone cyst or giant cell tumor. This variant should be approached as a conventional osteosarcoma.[4,5] Recognition of intraosseous well-differentiated osteosarcoma and parosteal osteosarcoma is important because these are associated with the most favorable prognosis and can be treated successfully with radical excision of the primary tumor alone.[6,12] Periosteal osteosarcoma has a generally good prognosis  and treatment is guided by histologic grade.[9,12]
Malignant fibrous histiocytoma (MFH) of bone is treated according to osteosarcoma treatment protocols. MFH should be distinguished from angiomatoid fibrous histiocytoma, a low-grade tumor that is usually noninvasive, small, and associated with an excellent outcome with surgery alone. One study suggests similar event-free survival rates for MFH and osteosarcoma.
Extraosseous osteosarcoma is a malignant mesenchymal neoplasm without direct attachment to the skeletal system. Previously, treatment for extraosseous osteosarcoma followed soft tissue sarcoma guidelines, though a retrospective analysis of the German Cooperative Osteosarcoma Study identified a favorable outcome for extraosseous osteosarcoma treated with surgery and conventional osteosarcoma therapy.
Schajowicz F, Sissons HA, Sobin LH: The World Health Organization's histologic classification of bone tumors. A commentary on the second edition. Cancer 75 (5): 1208-14, 1995.
Antonescu CR, Huvos AG: Low-grade osteogenic sarcoma arising in medullary and surface osseous locations. Am J Clin Pathol 114 (Suppl): S90-103, 2000.
Kaste SC, Fuller CE, Saharia A, et al.: Pediatric surface osteosarcoma: clinical, pathologic, and radiologic features. Pediatr Blood Cancer 47 (2): 152-62, 2006.
Bacci G, Ferrari S, Ruggieri P, et al.: Telangiectatic osteosarcoma of the extremity: neoadjuvant chemotherapy in 24 cases. Acta Orthop Scand 72 (2): 167-72, 2001.
Weiss A, Khoury JD, Hoffer FA, et al.: Telangiectatic osteosarcoma: the St. Jude Children's Research Hospital's experience. Cancer 109 (8): 1627-37, 2007.
Hoshi M, Matsumoto S, Manabe J, et al.: Oncologic outcome of parosteal osteosarcoma. Int J Clin Oncol 11 (2): 120-6, 2006.
Han I, Oh JH, Na YG, et al.: Clinical outcome of parosteal osteosarcoma. J Surg Oncol 97 (2): 146-9, 2008.
Rose PS, Dickey ID, Wenger DE, et al.: Periosteal osteosarcoma: long-term outcome and risk of late recurrence. Clin Orthop Relat Res 453: 314-7, 2006.
Grimer RJ, Bielack S, Flege S, et al.: Periosteal osteosarcoma--a European review of outcome. Eur J Cancer 41 (18): 2806-11, 2005.
Okada K, Unni KK, Swee RG, et al.: High grade surface osteosarcoma: a clinicopathologic study of 46 cases. Cancer 85 (5): 1044-54, 1999.
Staals EL, Bacchini P, Bertoni F: High-grade surface osteosarcoma: a review of 25 cases from the Rizzoli Institute. Cancer 112 (7): 1592-9, 2008.
Schwab JH, Antonescu CR, Athanasian EA, et al.: A comparison of intramedullary and juxtacortical low-grade osteogenic sarcoma. Clin Orthop Relat Res 466 (6): 1318-22, 2008.
Daw NC, Billups CA, Pappo AS, et al.: Malignant fibrous histiocytoma and other fibrohistiocytic tumors in pediatric patients: the St. Jude Children's Research Hospital experience. Cancer 97 (11): 2839-47, 2003.
Picci P, Bacci G, Ferrari S, et al.: Neoadjuvant chemotherapy in malignant fibrous histiocytoma of bone and in osteosarcoma located in the extremities: analogies and differences between the two tumors. Ann Oncol 8 (11): 1107-15, 1997.
Wodowski K, Hill DA, Pappo AS, et al.: A chemosensitive pediatric extraosseous osteosarcoma: case report and review of the literature. J Pediatr Hematol Oncol 25 (1): 73-7, 2003.
Goldstein-Jackson SY, Gosheger G, Delling G, et al.: Extraskeletal osteosarcoma has a favourable prognosis when treated like conventional osteosarcoma. J Cancer Res Clin Oncol 131 (8): 520-6, 2005.