| Abstract [eng] |
Thyroid nodules are detected in about 50% of adults who live in regions deficient in iodine. Although thyroid cancer is the most common oncological endocrine disorder, only 5% of the thyroid nodules are malignant. Papillary thyroid cancer (PTC) comprises 85 to 90% of cases of all histological types of thyroid cancer. Although PTC has a slow progression and good survival rates, 20% to 30% of patients have localized disease recurrences or distant metastases and about 1% of patients die from this disease. A fine needle aspiration biopsy (FNA) performed under ultrasound (US) guidance and a cytological examination of nodules remains the gold standard for the differential diagnostics of thyroid cancer. However, due to a well-differentiated nature of most thyroid cancers, 10 to 26% of samples are ascribed to cytologically indeterminate diagnostic categories (categories III, IV, V, according to the Bethesda system). In order to determine the exact diagnosis, diagnostic surgery is usually proposed for these patients; however, a histological examination of resected tissues confirms the diagnosis of thyroid cancer in only one-third of patients. In the absence of reliable preoperative diagnostic criteria, there is a risk of general, surgical intervention-related and thyroid surgery-specific complications including temporary or permanent vocal cord paralysis and temporary or permanent decrease in blood calcium levels. After surgery, replacement therapy with thyroxine is usually required for the rest of patients’ lives. Besides, psychological discomfort due to a 4 to 6 cm long scar in the neck may be experienced. These causes lead to high socioeconomic costs and encourage to search for new options of diagnostics and prediction that could potentially optimize patient selection for surgical treatment. Molecular genetic tests are among the most promising methods for the diagnostics of thyroid cancer and for the predictions of the disease course. The first works on the impact of BRAF mutations in oncological diseases were performed in studies of skin, colon and lung tumors. The link between BRAF mutations and PTC was confirmed in publications in 2003. A high V400E mutation specificity for PTC was noticed at that time. Therefore, Xing et al. had proposed BRAF V600E mutation testing for presurgical PTC diagnostics already in 2004. Although many publications on the applications of BRAF V600E mutation testing for PTC diagnostics and prognostication have appeared since that time, published data and recommendations remain controversial. Since the prevalence of BRAF V600E mutation in PTC tumors ranges from 30 to 80% depending on the geographical region, it can be stated that only the detection of mutation prevalence in the population under study can determine the applicability of this testing in clinical practice. The prevalence of BRAF V600E mutations in PTC in Lithuania has not been investigated so far. |
