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USMLE-Syndrome 06-17-2011 12:51 PM

Neoplasm association case
A 15-year-old boy is brought to the physician, because he has been limping on his left leg for the last 6 months. His left leg is painful and it is difficult for him to bear weight through it. The pain is constant and worse at night. He has a previous history of malignancy. Physical examination reveals a palpable mass with associated warmth over the distal femur. An X-ray reveals a sunburst pattern of diffuse bone spicules at the distal femur. What previous neoplasm did this patient most likely have?

Answer Choices
A. Acute lymphocytic leukemia
B. Astrocytoma
C. Non-Hodgkin lymphoma
D. Retinoblastoma
E. Wilms tumor

aksyonez 06-17-2011 02:43 PM

D. Retinoblastoma

1TA2B 06-17-2011 03:09 PM

I also think it's retinoblastoma. But I don't remember the link exactly!

aamand 06-17-2011 03:29 PM

Rb (Retinoblastoma) Protein
This is a Step 1 - like question.

You need to remember, Rb Tumor Suppressor Gene, which is inactivated in both retinoblastoma and osteosacrcoma.

The sunburst pattern in the vignette is a buzzword for osteosarcoma.

1TA2B 06-17-2011 03:45 PM


Originally Posted by aamand (Post 47321)
This is a Step 1 - like question.

You need to remember, Rb Tumor Suppressor Gene, which is inactivated in both retinoblastoma and osteosacrcoma.

The sunburst pattern in the vignette is a buzzword for osteosarcoma.

Yes I recall now! Thanks.

USMLE-Syndrome 06-18-2011 12:09 PM

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.

ratung 05-04-2012 06:01 AM


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