Evaluation of Hürthle cell–predominant fine-needle aspiration is often challenging. There is a wide spectrum of conditions that demonstrate Hürthle cell morphology, from inflammatory or reactive to malignant. Although cytomorphological criteria help distinguish reactive conditions from neoplasia/malignancy to some extent, there remains significant variability in diagnosis and risk of malignancy associated with the oncocytic (Hürthle) cell. The new classification in the fifth edition of the “WHO Classification of Endocrine and Neuroendocrine Tumors” that relates to the thyroid gland has replaced the term “Hurthle cells” with “oncocytic cells” and has categorized Hurthle cell carcinoma (now called “oncocytic carcinoma of the thyroid”) as a separate entity under differentiated thyroid carcinoma and not as a subtype of follicular thyroid carcinoma. The third edition (2023) of “The Thyroid Bethesda System for Reporting Thyroid Cytopathology (TBSRTC)” assigned a single name for each of the six diagnostic categories based on fine-needle aspiration cytology (FNAC): (I) nondiagnostic, (II) benign, (III) atypia of undetermined significance (AUS), (IV) follicular neoplasm, (V) suspicious for malignancy, and (VI) malignant. This resolves the confusion resulting from the prior editions, which assigned alternative names for three of the diagnostic categories. Thus, TBRSTC 2023 discontinued the previously used terms of “unsatisfactory,” “follicular lesion of undetermined significance (FLUS),” and “suspicious for a follicular neoplasm.” This chapter discusses the controversy of diagnosis of a oncocytic/Hurthle cell lesion on FNAC, whether it is neoplastic or nonneoplastic. It also discusses the limitations of cytology in the diagnosis of oncocytic/Hurthle cell lesions, the significance of the presence of oncocytic (Hurthle) cells in other pathologies, the risk of malignancy in indeterminate oncocytic/Hürthle cell nodules, and the possible role of morphological features in suggesting neoplasia or malignancy.