Abstract. Background: The cytopathologist plays an important role in the evaluation of thyroid cytomorphology in various neoplastic and non-neoplastic conditions. However, thyroid cytomorphology and the clinical implications of drug usage have rarely been discussed. Nonetheless, drugs used for different non-thyroid conditions may influence the hypothalamic-pituitary-thyroid axis and cause diverse cytomorphological patterns on aspiration smears. Clinicians should be informed of the presence or absence of specific underlying thyroid abnormalities detected on cytosmears which may warrant complete drug withdrawal, dose reduction, or change to different drug combinations. Besides these outcomes, interpreting thyroid cytomorphology, without a prior knowledge of antithyroid drug therapy, can be challenging and lead to misdiagnoses of neoplasm or malignancy. Cases: We present the thyroid cytomorphology of 3 different patients, each of whom was receiving a different drug (amiodarone, carbimazole, and carbamazepine) with biochemical, serological, and ultrasound correlations. We also briefly review the relevant literature. We conclude that a proper drug history is important while interpreting thyroid cytology in different clinical settings.

Keywords  ● Amiodarone ● Carbimazole ● Carbamazepine ● Cytomorphology ● Drugs ● Thyroid