الفهرس 
ContentsOnly 14 pages are availabe for public view
 |  | from | 158 |  |  |
| | | from | 158 | | |
Abstract
Nowadays thyroid nodular lesions represent common clinical problem, though the majority are benign, the challenge is the early detection and treatment of malignant ones. After considering ultrasonographic evaluation, F.N.A.C from suspicious thyroid nodular lesions is the gold standard for diagnosis with classifying these nodular lesions based on the Bethesda system.
Our study evaluated the diagnostic and prognostic utility of RAS point mutation detection (represented by NRAS in our work) in cytologically indeterminate nodules. Specimens from 100 cytologically indeterminate nodules were subjected to NRAS gene mutation testing at exon 12/13 and exon 61 by direct sequencing using (ABI 3500xl DNA Sequencer). The incidence of mutation detection was 34%, of which NRAS exon 61 mutations were the most common (76.4%).
In relation to preoperative Bethesda category, we found as regard cases of Bethesda class (III); only 27.1% were NRAS +ve. 38.7% of cases of class IV were NRAS +ve. 60% of cases of class V were NRAS +ve; denoting more incidence of NRAS mutation as the Bethesda category is increased. 90 cases were subjected to surgical treatment in our series (surgery correlation group).In relation to the results of postoperative pathology, only 19.6% of the benign cases were +ve for NRAS mutation (all were F.As). Of the malignant cases, 61.5% were +ve for NRAS mutation. 92.3% of F.V.P.T.C cases were +ve for NRAS mutation, 75% of F.T.C cases were +ve for NRAS 61, while 33.3% of P.T.C cases were +ve for NRAS. The probability of cancer in NRAS +ve cases in our study was 70.6%.So, most of our patients having malignant thyroid nodules especially follicular patterned (F.V.P.T.C & F.T.C) harbored NRAS mutation (61.5% for overall malignant nodules & 85.7% for follicular patterned carcinomas).
L.N metastasis was proved in only 35.9% of the malignant cases on postoperative histopathological examination, where 54.2% of NRAS +ve cases had no L.N metastasis denoting less incidence of L.N metastasis in NRAS +ve malignant thyroid nodules. Interestingly, the incidence of L.N metastasis in our study in follicular patterned carcinomas is low 28.6 % (6 out of 21 cases).
Conclusion: NRAS gene mutation testing is of great value in early diagnosis and treatment of patients with follicular patterned thyroid lesions (F.A, F.V.P.T.C &F.T.C) and can be used as a tumor marker in such patients. The NRAS mutation (mainly exon 61) was significantly associated with a high malignant rate in thyroid nodules. Performing RAS mutational testing as part of a panel with other genetic markers like BRAF and RET/PTC, can guide the extent of surgical management and lower the need of completion or redo thyroidectomy.