MON-449 Thyroid Microcarcinoma Histopathology Relevance

Abstract INTRODUCTION: Thyroid carcinoma is the most common endocrine neoplasia. The predominant histological variant is the papillary subtype. Tumors with 1 centimeter diameter or less are defined as papillary thyroid microcarcinoma (PTMC). The clinical diagnosis of PTMC is challenging. The evaluation of the gland includes mostly image methods and fine-needle aspiration (FNA). Nevertheless, the sensibility of these techniques, when compared to total thyroid histology, is less than desired. AIM OF THE STUDY: Recognize the real prevalence of papillary thyroid microcarcinoma (PTMC) based on histological evaluation of the total gland among a group of adults in Brasilia, Brazil, and compare the data with the clinical suspicion of PTMC established by FNA and ultrasonography (USG). PATIENTS AND METHODS: Retrospective cohort study based on medical records of 76 patients who underwent surgical thyroidectomy treatment for several types of thyroid diseases at the University Hospital of Brasilia - Brazil, from 2005 to 2015. A full inclusion of the surgical specimen was made and stained with hematoxylin and eosin. All of the preparations were evaluated by an expert pathologist. The histopathological report was compared to the previous clinical diagnosis, which was based on FNA and USG of the gland. In addition, the exams results were stratified by the Bethesda criteria. RESULTS: Seventy-six individuals with the histopathology diagnosis of PTMC were included (68 were females). A total of 65 FNA and 57 USG results were evaluated, 6 patients had only the histopathologic diagnosis of PTMC. A total of 52 patients had both USG and FNA of the thyroid. All of the patients that had USG records had at least one thyroid nodule, 52,6% of them had multiple nodules. Regarding the FNA results, only 9,2% were classified as Bethesda I; 21,5% as Bethesda II; 7,7% Bethesda III; 7,7% Bethesda IV; 10,8% Bethesda V; 43,1% Bethesda VI. At this cohort, 19 patients were false negatives. The sensibility of FNA for diagnosis of PTMC was 67,79%. CONCLUSION: Despite careful evaluation of the patients, there might have false negatives results. Total thyroid total inclusion of surgical specimen is not a routine diagnostic tool, making less invasive new diagnosis methods desirable.