MMDIT (DDIT3 (12q13) Rearrangement by FISH)
Order Code: MDDIT
CPT Code: 88377-TC, 88377-26
Effective January 20, 2021, MLabs will now offer MMDIT (DDIT3 (12q13) Rearrangement by FISH) [MDDIT]. See below for details.
Test Usage/Test Limitations: DDIT3 (formerly CHOP) encodes a transcription factor involved in adipogenesis and erythropoiesis. Rearrangements involving this gene are characteristic of myxoid liposarcoma. Morphologically, myxoid liposarcomas demonstrates uniform, small spindled cells within a myxoid stroma with distinctive arborizing capillaries. A subset of myxoid liposarsomas show progression to round cell morphology, associated with a poorer prognosis. Approximately 95% of myxoid liposarcomas bear a t(12;16)(q13;p11) rearrangement that results in the fusion of the N-terminal transactivation domain of FUS and the full length of DDIT3. In the remaining cases, there is a similar rearrangement involving DDIT3 and EWSR1. The detection of DDIT3 rearrangements can be useful in diagnosing myxoid liposarcoma – including uncommon histologic variants – and in distinguishing this sarcoma from other mesenchymal tumors that may be considered in the differential diagnosis.
Specimen Requirements: A formalin-fixed, paraffin-embedded tissue block (containing sufficient neoplastic cells) is preferred. Unstained slides (3 slides cut at 4-microns) with associated H&E-stained slide are also acceptable. Decalcified tissue or tissues with other fixatives will be accepted and the assay attempted; however, these specimens may result in failed testing due to degraded nucleic acid. Both blocks and slides should be stored at room temperature.
Test Methodology: Fluorescence In Situ Hybridization (FISH)
Analytic Time: 3 – 10 days