BACKGROUND Diverse cytological patterns of thyroid lesions may occur in the thyroid gland for its various diseases. The thyroid lesions may be nonneoplastic lesions or neoplastic lesions. Most of the thyroid lesions clinically present as thyroid swellings either as thyroid nodules or as diffuse enlargement of the gland itself. Fine Needle Aspiration Cytology (FNAC) is a rapid, easy to perform, minimally invasive and cost-effective first line high diagnostic accuracy test for cytological evaluation of thyroid lesions with minimum complications. The thyroid gland is easily accessible for Fine Needle Aspiration (FNA) procedure due to its superficial location. The accurate cytological diagnosis of the thyroid lesions can direct the treatment modalities of the lesions and reduce unnecessary thyroid surgeries. AIMS AND OBJECTIVES A hospital-based study to determine the cytological patterns of thyroid lesions by FNAC and to correlate the cytological and histopathological diagnosis wherever possible. MATERIALS AND METHODS The study was based on "FNAC analysis of 100 thyroid lesions presented as thyroid swellings" (study group) in the period of two (02) years from June 1, 2014, to May 31, 2016, in the cytopathology section of the Pathology Department of Tezpur Medical College and Hospital, Tezpur, Assam. Histopathological correlation was done in the surgically treated thyroid lesions of the study group. RESULTS AND OBSERVATIONS Female patients (87) comprised majority of thyroid lesions (87.00%), while male patients (13) were only 13.00% of thyroid lesions with a male and female patients' ratio of 6.69:1 in the study group. Maximum patients with thyroid lesions, irrespective of sex in the study group were in the age group of 31-40 years. The youngest patient in the study group was a 7 years old girl diagnosed as lymphocytic thyroiditis and the oldest patient in the study group was a 73 years old female diagnosed as colloid goitre. Out of 100 thyroid lesions in the study, FNA smears of 05 thyroid lesions were inadequate for cytological reporting either due to inadequate aspirated materials or haemorrhagic smears. Out of remaining 95 thyroid lesions in the study, which had adequate FNA smears for cytological reporting, there were 84 (88.42%) non-neoplastic lesions and 11 (11.58%) neoplastic lesions with a non-neoplastic and neoplastic ratio of 7.64:1. Colloid goitres were the commonest non-neoplastic thyroid lesions in the study. Out of the 8 thyroid lesions diagnosed as thyroiditis in the study, granulomatous thyroiditis (04) were the commonest. Benign tumours (6.32%) were found to be more common than malignant ones (4.21%) with a benign and malignant tumours ratio of 1.50: 1 in the study. Follicular neoplasms were the commonest benign tumours and papillary thyroid carcinomas were the commonest malignant tumours amongst the studied thyroid lesions. One thyroid lesion of medullary carcinoma was also diagnosed. Among all thyroid lesions in the study, with adequate FNA smears for cytological reporting, 70 (73.68%) thyroid lesions were goitres with or without secondary changes, 06 (6.32%) thyroid lesions were benign neoplasms, 01 (1.05%) thyroid lesion was suspicious and 04 (4.21%) thyroid lesions were malignant neoplasms. FNAC studies done only on 15 thyroid lesions in the study group were available for histopathological studies and showed 93.33% diagnostic accuracy. The histopathological findings of that 15 thyroid lesions showed 11 non-neoplastic (73.33%) and 04 (26.67%) neoplastic lesions. On comparison of FNAC and histopathology study reports of these 15 thyroid lesions, histopathology confirmed all the 11 non-neoplastic lesions (10 were simple colloid goitres and 1 thyroglossal cyst) and 3 out of 4 neoplastic lesions diagnosed on FNAC. Out of 3 thyroid lesions diagnosed as follicular neoplasms on FNAC, 2 thyroid lesions confirmed the diagnosis, but one was confirmed as follicular variant of papillary carcinoma on histopathology. One thyroid lesion diagnosed as papillary carcinoma on FNAC was confirmed on histopathology. DISCUSSION Today, FNAC is practiced worldwide for rapid and accurate preoperative diagnosis of thyroid lesions. There are several studies regarding cytological evaluation of thyroid lesions by FNA and literatures claiming the usefulness of thyroid cytology. This study was a hospital-based study that described the cytological patterns of thyroid lesions that encountered in this institute within the study period and histopathological diagnosis comparison wherever possible. The results and observations of this study were most comparable with the previous studies by other researchers. The limitation of the study was that due to absence of representative aspirated materials of 05 thyroid lesions couldn't be diagnosed in the appropriate manner. FNAC diagnoses of only 15 thyroid lesions were available for histopathological study. All patients performed FNAC for thyroid lesions during the study period in our institute couldn't be followed up, probably these patients attended other centres later. CONCLUSION FNAC has high sensitivity in cytological diagnosis of thyroid lesions and accurate cytological diagnosis may be considered as a primary line of investigation of thyroid lesions and its management. Due to its high accuracy, sensitivity and specificity, the study established its usefulness for proper line of management of the patients with thyroid lesions.
