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Interpretive Handbook

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Test 84456 :
Myxoid/Round Cell Liposarcoma 12q13 (DDIT3 or CHOP) Rearrangement, FISH, Tissue

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Myxoid/round cell liposarcoma is the second most common subtype of liposarcoma, accounting for more than one third of all liposarcomas and representing about 10% of all adult soft-tissue sarcomas. Myxoid/round cell liposarcoma is described as a malignant tumor composed of uniform round to oval shaped primitive nonlipogenic mesenchymal cells and a variable number of small signet-ring lipoblasts in a prominent myxoid stroma with a characteristic branching vascular pattern.

 

A unique chromosome translocation, t(12;16) (q13;p11), resulting in a fusion of the DDIT3 gene (also known as CHOP or GADD153) on chromosome 12 and the FUS gene (also referred to as TLS) on chromosome 16, is the key genetic aberration in myxoid/round cell liposarcoma. More than 90% of myxoid/round cell liposarcoma are cytogenetically characterized by this translocation. In rare cases, a variant t(12;22)(q13;q12) has been described in which DDIT3 (CHOP) fuses with EWS, a gene highly related to FUS.

Useful For Suggests clinical disorders or settings where the test may be helpful

As an aid in the diagnosis of myxoid/round cell liposarcoma by detecting a neoplastic clone associated with gene rearrangement involving the CHOP gene region at 12213.

Interpretation Provides information to assist in interpretation of the test results

A neoplastic clone is detected when the percent of cells with an abnormality exceeds the normal cutoff for the CHOP probe. A positive result is consistent with a subset of myxoid/round cell liposarcoma. A negative result suggests no rearrangement of the CHOP gene region at 12q13. However, this result does not exclude the diagnosis of myxoid/round cell liposarcoma.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test is not approved by the FDA and it is best used as an adjunct to existing clinical and pathologic information.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Turc-Carel C, Limon J, Dal Cin P, et al: Cytogenetic studies of adipose tissue tumors. II. Recurrent reciprocal translocation t(12;16)(q13;p11) in myxoid liposarcomas. Cancer Genet Cytogenet 1986;23(4):291-299

2. Aman P, Ron D, Mandahl N, et al: Rearrangement of the transcription factor gene CHOP in myxoid liposarcomas with t(12;16)(q13;p11). Genes Chromosomes Cancer 1992;5(4):278-285

3. Antonescu CR, Elahi A, Humphrey M, et al: Specificity of TLS-CHOP rearrangement for classic myxoid/round cell liposarcoma: absence in predominantly myxoid well-differentiated liposarcomas. J Mol Diagn 2000;2(3):132-138

4. Antonescu C, Ladanyi M: Myxoid liposarcoma. In Pathology and Genetics of Tumours of Soft Tissue and Bone. World Health Organization Classification of Tumours. Vol 5. Edited by CDM Fletcher, K Unni, F Mertens. Lyon, IARC Press, 2002, pp 40-43

5. Meis-Kindblom JM, Sjogren H, Kindblom LG, et al: Cytogenetic and molecular genetic analyses of liposarcoma and its soft tissue simulators: recognition of new variants and differential diagnosis. Virchows Arch 2001;439(2):141-51


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