ObjectiveThe association between follicular carcinoma and iodine deficiency (ID) is based on epidemiological studies and their inherent biases. The aim of the study was to assess the impact of long-term ID exposure on thyroid nodule cytology and final pathology in a distinct group of patients within a single institution. MethodsEthiopian origin patients were compared to an aged-matched group of non-Ethiopian patients. Demographics, risk factors, clinical presentation, cytology and pathology were collected and compared. Final outcomes were cytology and pathology distribution. ResultsA total of 489 (246 Ethiopian, 243 control) nodules of 461 patients (230 and 231 respectively) were included. Ethiopian patients had lower rates of thyroid cancer risk factors (p=0.05). Cytology analysis demonstrated significant group differences (p=0.03), as Ethiopian patients had higher rates of benign cytology (85% vs. 75.7%, respectively).Pathology analysis demonstrated a significantly lower malignancy rate among Ethiopian patients (39.2% (20/51) vs. 63.3% (31/49), p=0.027, respectively). The Ethiopian group had a significant higher rate of follicular carcinoma compared to the control group (25% [5/20] vs. 3.2% [1/31], p=0.034, respectively) and lower rates of papillary thyroid carcinoma (25% [5/20] vs. 61.3% [19/31], p=0.017, respectively). ConclusionsThe association between ID and FC exists years following immigration and exposure to a better iodine diet, implying that differentiation may be affected in earlier stages and levels of exposure.