Thyroid follicular lesion of undetermined significance - the risk of malignancy in postendemic area
D. Slowinska-Klencka, S. Sporny, E. Wozniak, B. Popowicz & M. Klencki
The introduction of the new classification of the thyroid FNAB results which stratifies the risk of malignancy of thyroid follicular lesions is of special interest in endemic and postendemic areas. In such regions patients with non-neoplastic nodular goitre predominate and nodules diagnosed previously as follicular neoplasm showed to be thyroid cancer less frequently than in iodine-rich areas.
The aim of the study was to evaluate the frequency of follicular lesion of undetermined significance (FLUS) diagnosis and to assess the risk of malignancy in this category in postendemic areas.
In 2010 our Department adopted six-category diagnostic approach in reporting thyroid FNAB results that was based on National Cancer Institute (NCI) recommendations. In this system aspirates from follicular lesions are classified into 2 categories: FLUS and SFN (suspicious for a follicular neoplasm). The study included 5480 patients in whom 8877 nodules were biopsied between May 2010 and November 2011.
There were 218 nodules diagnosed as FLUS (2.5%) in 203 patients, including 4 cases of the oxyphilic type. In 92 cases the follow-up was determined: 51 patients underwent control FNAB and 48 patients were treated surgically (7 patients were operated after control FNAB). The results of control FNAB showed: papillary cancers in 2 cases, lesion suspicious for papillary cancer - 1, SFN - 1, FLUS - 19 and benign lesions - 24. In 4 patients control FNAB was non-diagnostic. Histopathological examination showed papillary cancer in 4 patients (in 1 patient it was microcancer in the contralateral lobe), follicular adenoma in 4 patients, chronic thyroiditis in 3 patients and hyperplastic nodule in 37 patients. In total the thyroid cancer was found in 4.3% (4/92) of verified patients with FLUS.
In postendemic areas the incidence of thyroid cancer in the nodules diagnosed as FLUS is lower than 515% reported by the NCI. It suggests that such lesions should be followed up clinically without prompt surgical intervention.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector