Introduction: Hashimoto’s/Lymphocytic thyroiditis is a common autoimmune disorder which has female preponderance. Autoimmune thyroiditis is considered as a complex interaction and interplay between various genetic and non-genetic factors. Molecular basis of Hashimoto’s thyroiditis is not known. Fine needle aspiration cytology being first line of investigation for thyroid lesions is helpful in diagnosing these lesions as well. However, few potential pitfalls in cytology may lead to cytohistologic discordance. Materials and methods: This is a retrospective study of one year where all histologic proven cases of Hashimoto’s/ Lymphocytic thyroiditis with their corresponding fine needle aspiration cytology slides from pathology database were studied. All FNACs were analyzed in depth and reviewed for cytohistologic correlation. The reasons of cytohistologic discrepancies and discordant cases were analyzed. The genetics of autoimmune thyroiditis was also reviewed from literature. Results: Out of total 38 cases of HT/LT analyzed in this study, 89% were females and 11% were males. Mean and median age was found to be 44.4 years and 44 years respectively. Correlation of cytology and histology showed that 50% FNACs’ correlated with their respective histologic diagnosis. Major causes of the discrepancies and discordance are reporting on suboptimal smears, cystic fluid samples, and giving over emphasis on a single cytologic feature in rare cell clusters. Conclusion: Autoimmune thyroiditis is frequently encountered lesion. Fine needle aspiration cytology is useful in deciding the management of thyroid lesions. In order to restrict the discrepancies and cytodiagnostic errors, one must adhere to the adequacy criterion along with primary fixation, quality of the smear and cellularity. Cytopathologists should be aware of the possible pitfalls and differentiating clues when overlapping features between different lesions are encountered. Also an integrated multidisciplinary approach can be used to minimize potential pitfalls. Many a time the condition can be diagnosed after death as seen in case of few sudden deaths. The unexpectedly brought in thyroid dysfunction is expected in such cases. So the forensic pathologist must keep this entity in mind while dealing with cases of sudden death.

Keywords: Autoimmune; Cyto-histologic discordance; Fine needle aspiration cytology; Genetics; Hashimoto’s thyroiditis