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| Author(s): |
Erika Urbano de Lima
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD) |
| Defense date: | 2012-08-17 |
| Examining board members: |
Suemi Marui;
Rosalinda Yossie Asato de Camargo;
Janete Maria Cerutti
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| Advisor: | Suemi Marui |
| Abstract | |
Thyroid cancer is the most common endocrine malignancy, accounting for 1- 2% of thyroid malignancies. Currently, the molecular pathogenesis of papillary thyroid carcinoma (PTC) has been linked to aberrant activation of the MAPK signaling pathway, triggered by mutations in several oncogenes. Of these, the p.V600E mutation of BRAF gene is the most frequent, being observed in 30%-80% of cases. Several studies have shown that the presence of this mutation is associated with an increased aggressiveness of the tumor and, consequently, a less favorable prognosis, making it an important set PTC. However, few methods used for analyzing samples from fine needle aspiration (FNA) of thyroid nodules were satisfactory regarding cost, time and sensitivity. The objectives of this study were to standardize the DNA extraction from samples obtained from ultrasound (US)-guided FNA of thyroid nodules; validate and determine the efficiency and cost-time of real-time PCR genotyping technique to detect p.V600E mutation from samples of FNA of thyroid nodules, to assess the prevalence of the mutation p.V600E mutation in patients with PTC, correlate the presence of the p.V600E mutation with clinical and histopathological features of higher aggressiveness and finally analyze the sensitivity, specificity and accuracy of cytological diagnosis in conjunction with molecular analysis of the p.V600E mutation in FNA material. Our series consisted of 224 patients, all underwent thyroidectomy, whose preoperative cytology was indeterminate (Bethesda classes III to V) or Bethesda VI (papillary carcinoma). We evaluated clinical data and hormone (TSH) and autoimmunity (anti-TPO and anti-TG), and the sonographic features (size, structure, echogenicity, presence of microcalcifications and halo and vasculature). The histological data were tumor size, histological variant, capsule invasion, lymphatic and vascular invasion, extrathyroidal extension, multicentricity and presence of malignant lymph nodes at surgery. Results: The patients were divided into benign (n:122) and malignant group (n:102), according to the final histological diagnosis. Malignant group had a mean age lower than the benign group (48.9 vs 54.2 years, p=0.008). There were no differences between groups regarding serum TSH (p=0.467), anti-TPO (p=0.535) and anti-TG (p=0.730). According to US characteristics, size and volume of the nodules were higher in the benign group (3.0 vs 2.6 cm and 12.38 cm 3 vs 14.5, p=0.008 and p<0.001, respectively). The nodules that showed hypoechogenicity, as well as the composition of solid nodules, the presence of microcalcifications, absence of hypoechoic halo and presence of central vascularization showed statistically higher frequency of malignancy. In the logistic regression model, older age, solid nodule without hypoechoic halo and microcalcifications were variables that influenced jointly in the presence of malignancy. In cytological diagnosis 78.6% (176/224) of nodules were evaluated as class III, IV and V, and of these 35.8% (63/176) had final histological diagnosis of malignant. The p.V600E mutation were identified in FNA material in 67.7% (69/102) of patients in malignant group, present in 70.3% (45/64) of papillary carcinoma classic variant and 69.7% (23/33) of follicular variant of papillary carcinoma, and all findings are confirmed in 100% of the samples through sequencing of the material obtained from the surgical tumor (fresh or paraffin). In patients with confirmed PTC (n:98), we compared patients with and without the mutation p.V600E according to clinical, histological poor prognosis, lymph node metastasis, and TNM stage according to AJCC. Only the presence of older age were significantly associated with the presence of the mutation p.V600E (p=0.041). We compared the cytological diagnosis based on the Bethesda classification and mutation analysis with the histological diagnosis p.V600E, the \"gold standard\" for diagnosis of PTC. Sensitivity, specificity, accuracy, positive and negative predictive value of cytological diagnosis was 67.4%, 94.4%, 79.8%, 93.3% and 71.2% respectively. Analysis of p.V600E mutation alone showed similar results to the cytological diagnosis, but we observed that the combination of cytological diagnosis with mutation analysis significantly improved all parameters analyzed. The presence of the mutation p.V600E in our series was not a single factor associated with worse prognosis of PTC. A larger number of patients and long term follow-up, adding to careful clinicalmorphological with p.V600E and mutation detection using multivariate analyzes are needed to clarify the independent prognostic significance of this mutation. Similar studies are also needed to find a combination among clinical and US, with p.V600E mutation detection in FNA material to decide the best surgical approach (AU) | |
| FAPESP's process: | 09/03321-7 - Analysis of V600E BRAF mutation in fine needle aspiration from thyroid nodule with suspicious or pappilary carcinoma diagnosis. |
| Grantee: | Erika Urbano de Lima |
| Support Opportunities: | Scholarships in Brazil - Master |