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RET encodes a receptor tyrosine kinase involved neural crest development. Oncogenic RET mutations occur frequently in medullary thyroid carcinoma (MTC). Approximately 50-60% of sporadic MTC harbor somatic RET mutations. The presence of these mutations is associated with an inferior prognosis and more aggressive disease. Germline RET mutations are associated with multiple endocrine neoplasia (MEN) 2 or familial medullary thyroid carcinoma. Multi-kinase inhibitors (MKI) including vandetanib and cabozantinib are FDA-approved for the treatment of metastatic or unresectable MTC (regardless of RET mutation status). Reported response rates to these agents range from 20%-45%. These drugs are often associated with toxicities – some (e.g. impaired wound healing, fistula formation, hemorrhage) related to inhibition of other tyrosine kinases, particularly vascular endothelial growth factor receptor 2 (VEGFR-2). Several selective tyrosine kinase inhibitors (TKI) with much greater RET inhibitory potency have been developed including LOXO-292, BLU-667 and RXDX-105. These drugs have shown promising efficacy with significantly lower toxicity in RET-mutated MTC.
Interpretive report provided.
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
For formalin-fixed, paraffin-embedded tissue, a block containing an area with a high percentage of neoplastic cells (for micro-/macro-dissection) is preferred. Unstained, UNBAKED slides (5-8, 10-micron slides; 10-15 if few neoplastic cells are present) with associated H&E stained slide are also acceptable. Decalcified tissue or other fixatives will be accepted and the assay attempted, however these may result in failed testing due to degraded nucleic acid. Both blocks and slides should be stored at room temperature. A Diff-Quik or Papanicolaou stained aspirate smear (preferable containing a high percentage and overall amount of neoplastic cells) is also acceptable. Store at room temperature.