Spectrum of Thyroid Lesions in A Tertiary Care Hospital using Bethesda System for Reporting Thyroid Cytopathology

Background: Thyroid Fine Needle Aspiration (FNA) has been widely used as a first line investigation to assess thyroid nodules, as it is rapid, cost effective, safe and reliable. To bring uniformity and standardization in thyroid cytology reporting, “The Bethesda System for Reporting Thyroid Cytopathology” (TBSRTC) was introduced and it is gaining acceptance. This study has been undertaken to evaluate the reproducibility using TBSRTC system while reporting thyroid FNACs and to find out the utility of Bethesda system after correlating with the histopathology. Methods: A retrospective study was conducted in which 173 cases of thyroid aspirates were reclassified according to TBSRTC in to six categories by cytologist. Results: A total of 173 thyroid lesions were analysed. Category wise distribution of aspirates was Non diagnostic (ND) 9 (5.20%), Benign (BN) 145 (83.81 %), Follicular neoplasm (FN) 9 (5.20%), Follicular lesion of uncertain significance (FLUS) Nil, suspicious of malignancy(SM) 1(0.57 %) and malignant category 9 (5.20 %). Age and sex wise distribution was interpreted.Thyroid diseases were more prevalent in women and most common age group affected was 3rd to 4th decade. Out of 164 lesions which were satisfactory for evaluation,120 (73.17 %) were simple goitre , 15(9.14 %) were of thyroiditis, 6 (3.65%) were toxic goitre, 4 (2.43%) were thyroid cysts & 19 (11.57 %) were neoplasms of which benign included 1 (0.6%) Hurthle cell neoplasm and 8 (4.87 %) follicular neoplasm. Malignant lesions were 8 (4.87%) papillary carcinoma, 1 (0.6%) anaplastic carcinoma and 1(0.6%) medullary carcinoma. Conclusions: It was observed that standardized nomenclature of the Bethesda system has brought much needed clarity in thyroid FNAC reporting. Along with malignant category, the FLUS, FN and SM categories carry higher malignancy risk.


Introduction
Thyroid nodule is a common clinical condition and nearly 85 to 90% of them are benign lesions. [1,2] Thyroid FNA has been widely used as a firstline investigation to assess thyroid nodules, as it is rapid, cost effective, safe and reliable. [3] It is important that cytology report is unambiguous and clinically useful. It has been observed that thyroid FNAC smears terminologies vary significantly from one laboratory to other, sometimes from one cytologist to other in the same institution. This is creating confusion in some cases and has become an obstacle in sharing information amongst different institutions. [4,5] This issue of terminology related to thyroid cytology was addressed at National Cancer Institute (NCI) which hosted "NCI thyroid FNA state of the science conference" which led to the formation of "The Bethesda System for Reporting Thyroid Cytopathology" (TBSRTC). [6] The TBSRTC system is presently being widely used in US and several European Countries, and in India also it is gaining acceptance. This study has been undertaken to evaluate the reproducibility using TBSRTC system while reporting thyroid FNACs and to find out the utility of Bethesda system as there is lack of such data in this region.

Materials and Methods
Details of all the thyroid FNAC cases done from Jan 2009 to November 2014 in a tertiary care hospital were retrieved from archives of cytology section. Experienced cytologist with experience in cytology reporting and self learned the different aspects of TBRTC, reviewed the slides. All the clinical details and available radiological and thyroid function test results which were noted down in the original cytology request forms were provided to cytologist. The FNA smears were reclassified in a double blinded fashion into six categories as per TBSRTC. e. Suspicious for malignancy(SM); Smears in this category were mainly cellular with crowded cell groups exhibiting nuclear and cytoplasmic pleomorphism with some occasional single atypical cells. In the context of suspicious papillary carcinoma rare presence of nuclear enlargement, grooves, overlapping and/or pseudoinclusions along with thick colloid were considered suspicious.

Annals of
f. Malignant (MGT); Lesions were classified into this category if they were frankly malignant with type specification. The spectrum of all the thyroid lesions was classified as per the above six categories.
The various thyroid lesions in all the categories are described in Table 2. The female to male ratio in our study was 3.5 : 1. The youngest patient was 11 year female child with simple colloid goitre. The oldest patient was 80 years male patient with papillary carcinoma. Most common age group affected with thyroid lesions was 3 rd to 4 th decade and most common thyroid lesion was simple colloid goitre which was most commonly seen in 3 rd to 4 th decade.
Least common age group affected was 71-80 years. Most common lesion in 7 th to 8 th decade was colloid goitre with cystic change as shown in Table 3. Most common thyroid malignancy was Papillary carcinoma seen most commonly in 6 th to 7 th decade. Most common Inflammatory thyroiditis was Hashimoto's thyroiditis. The most common thyroid lesion in Pediatric age group was simple colloid goitre.   Thyroid cyst -- Hashimoto's thyroiditis --

Discussion
Fine needle aspiration cytology is considered standard diagnostic test for the diagnosis of thyroid lesions . There is a lack of uniformity which is a big hindrance in interpreting the reports of thyroid FNA. Institutional, personalized and descriptive terminologies without proper categorization is leading to confusion in the minds of treating physicians. TBSRTC system was introduced after the Bethesda meeting of cytopathologists, endocrinologists, surgical pathologists, radiologists and surgeons to put in place, a universal reporting system through which cytologists and physicians could understand each other and could help in predicting the prognosis by estimating the malignant potential of the individual category. [7,8,9] An attempt was made in the present study, to reclassify the 173 cases according to the new proposed six tier diagnostic classification system in reporting thyroid FNA results as Non diagnostic (ND) 9 (5.20%), Benign (BN) 145 (83.81%), Follicular neoplasm (FN) 9 (5.20%),Follicular lesion of uncertain significance (FLUS) Nil, Suspicious of malignancy (SM) 1 (0.57 %) and malignant category 9(5.20). TBSRTC also assists in calculating the malignancy risk for eash category which is essential for treatment decision. Benign category was maximum in our study similar to the other studies (  [10] , Uma et al [11] and Bhatta et al. [12]

Conclusion
Fine needle aspiration cytology is standard diagnostic test for the diagnosis of thyroid lesions with a high diagnostic yield, accuracy, sensitivity & specificity. Fine needle aspiration cytology is a cost effective procedure that provides specific diagnosis rapidly with minimum complications. It was observed that standardized nomenclature of the Bethesda system is more systematic and brought much needed clarity in thyroid FNAC reporting. Along with malignant category, the FLUS, FN and SM categories carry higher malignancy risk. Close follow up of the patients and surgical intervention option has to be considered in FLUS, FN and SM categories. However, a prospective study with large number of cases for cytohistopathological correlation may be needed to improve our understanding of these TBSRTC categories.