What is Endocrinology - How are thyroid cancer diagnoses and prognoses affected by molecular markers?
The use of molecular markers that can be detected in thyroid biopsy aspirates has improved practitioners' capacity to identify malignancy in thyroid nodules with uncertain FNA cytology (average malignancy risk ,25 percent ). There are two commercial tests that estimate the likelihood of developing cancer using various techniques. The Veracyte, Inc.-developed Afirma test uses microarray analysis on a gene set with a high negative predictive value (NPV) of 93% and a 40%–50% positive predictive value (PPV) for suspicious nodules. With the use of this test, it is possible to predict benign lesions and prevent needless diagnostic surgery. The miRInform test by Asuragen, Inc. examines thyroid nodule aspirates for particular RNA fusion transcripts (RET/PTC1, RET/PTC3, and PAX8/PPARg) and DNA mutation markers (KRAS, HRAS, NRAS, and BRAF mutations) that are specific for thyroid cancer. Although benign follicular adenomas can also harbour RAS mutations, thyroid carcinoma is the disease for which they have a PPV of about 85%. The remaining markers in this panel are all functionally 100% predicative of cancer. However, because thyroid tumours may have genetic mutations that are missed by this test, their sensitivity is rather low. Compared to other mutations discovered in differentiated thyroid cancer (DTC), BRAF is present in between 30 and 60 percent of papillary thyroid cancer (PTCs) and is associated with worse overall prognosis, lymph node metastases, radioiodine resistance, and more local invasion.
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