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Old 06-18-2011
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Option D (Retinoblastoma) is correct. A sunburst pattern at the distal femur is characteristic of osteosarcoma, the most common primary bone malignancy that typically affects individuals 10 to 25 years of age. Although most cases are idiopathic, there is an established molecular mechanism between retinoblastoma and osteosarcoma. Questions have arisen about the utility of screening patients with retinoblastoma for osteosarcoma occurrences. At present, however, screening is not performed.

Option A (Acute lymphocytic leukemia) is incorrect. ALL is associated with Down syndrome.

Option B (Astrocytoma) is incorrect. Astrocytomas are the most common primary CNS malignancy of children. It has a slow, protracted course and presents with signs and symptoms of raised intracranial pressure.

Option C (Non-Hodgkin lymphoma) is incorrect. NHL is not associated with development of osteosarcoma in the future.

Option E (Wilms tumor) is incorrect. A Wilms tumor is the most common renal tumor in children. It is associated with aniridia and hemihypertrophy.

High-yield Hit 1
Osteosarcomas are malignant mesenchymal neoplasms in which the neoplastic cells produce osteoid. Excluding multiple myeloma, a tumor of B cells (Chapter 12), osteosarcoma is the most common primary malignant tumor of bone. Although once they were universally fatal, recent therapeutic advances have dramatically improved the outlook for these neoplasms. Several different variants of osteosarcoma exist; these can be distinguished from one another by clinical presentation, radiographic findings, histology, and, most importantly, prognosis. In the simplest classification scheme, osteosarcomas can be divided into primary forms, which arise de novo, and secondary forms, which arise as a complication of a known underlying process, such as Paget disease of bone or a history of radiation exposure.

From Robbins Basic Pathology 7E by Kumar et al
High-yield Hit 2
A number of different forms of primary osteosarcoma have been recognized. These include the "conventional" form, which accounts for about three fourths of the cases, and several less common variants. Conventional osteosarcomas occur most often during the second decade of life. Although they may arise anywhere in the body, the most common site of origin is the area around the knee, specifically the distal femur and proximal tibia. Males are affected more often than are females. Although the cause of most primary osteosarcomas remains unknown, as with other malignant neoplasms, mutations appear to be important in their pathogenesis. Mutations in the TP53 tumor suppressor gene, in particular, are present in many sporadic osteosarcomas. Overexpression of the MDM2 oncogene is also noted in many cases. MDM2 protein binds to and inactivates the TP53 gene product. Germ-line mutations in the retinoblastoma gene predispose patients to develop osteosarcomas as well as hereditary retinoblastomas. In addition, loss of heterozygosity at 3p, 13q, 17p, and 18q has also been noted. The high incidence of loss of heterozygosity at 3p suggests the existence of a tumor suppressor gene at this locus.
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