Introduction: Thyroid gland is very often subjected to FNAC as thyroid enlargement is a common clinical problem and also due to its easy accessibility for the procedure. Hurthle cells are commonly encountered in thyroid aspirates from varied etiology. Aim of the Study: To find the significance of Hurthle cells in thyroid cytology and to note the cytological features that would differentiate reliably between different lesions containing Hurthle cells. Materials and Methods: This was a two yearstudy conducted in the Department of Pathology, at NRI Institute of Medical Sciences, Visakhapatnam. A total of 858 thyroid aspirates were done of which 240 cases showed Hurthle cells. These 240 cases consisted of the study group in which histopathology examination was done in 107 cases. There were 229 female and 11 male patients in the age groups of 10 to 70 years. Observations and Results: Hurthle cells were seen in 240 (11.6%) cases. Non neoplastic and neoplastic Hurthle cell lesions comprised 222 (92.5%) and 18 (7.5%) cases respectively.There was a female predominance with the male to female ratio being 1:20. There were 201 cases (83.7%) with non neoplastic and 39 (16.2%) with neoplastic etiology. Hashimoto’s thyroiditis, nodular goiter and follicular adenomas commonly showed Hurthle cells. For Hurthle cell lesions, important cytological features were predominantly monomorphic Hurthle cell population, macronucleoli and absence of inflammatory cells. There was good agreement between the cytology and histopathological examination. Conclusion: Hurthle cells are seen in various lesions of thyroid. The presence of>50% of Hurthlecells in an aspirate indicates a Hurthle cell neoplasm.Aspiration cytology in Hurthle cell lesions can differentiate non neoplastic lesions from neoplastic lesions with high accuracy, but differentiation between benign and malignant neoplasms is less reliable.

Keywords: Thyroid FNAC; Hurthle Cells; Hashimoto’s Thyroiditis; Thyroid Histopathology.