Oncocytes in Thyroid Aspirates—Implications of Clinical Parameters and Cytologic Diagnosis

ImportanceThe clinical significance of oncocytes in thyroid aspirate is uncertain, leading to inconsistent and possible over-treatment.ObjectiveTo determine the predictive significance of clinico-radiological parameters and cytologic diagnosis on the risks of malignancy (ROM) and neoplasia.DesignData of thyroid aspirates with the presence of oncocytes were reviewed for outcomes and clinical-radiological-pathological parameters.SettingThree regional institutes performing thyroid surgery and investigations.ParticipantsFrom a population base of 1.3 million across a 9-year period, totaling 371 aspirates with oncocytes with an 85.0-month average follow-up.InterventionFine-needle aspiration of thyroid.ResultsOn clinical follow-up, the ROM for Bethesda categories C1-C6 was 15.4%/2.7%/9.2%/6.9%/37.5%/100%, while the risk of neoplasm (considering thyroidectomy follow-up) was 45.5%/23.8%/56.3%/61.9%/50%/100%, including 52 oncocytic follicular lesions (4 carcinomas and 48 adenomas) and 26 other carcinomas/malignancies. C5+ diagnoses were associated with malignancy (<i>P</i> = .003), and C3+ was associated with neoplasm on thyroidectomy (<i>P</i> = .006). Malignant/neoplastic outcomes did not correlate with sex or age (<i>P</i> > .05). High free triiodothyronine/free thyroxine levels were associated with a benign clinical outcome (<i>P</i> = .001). Cystic change on ultrasound was associated with a lower malignancy (<i>P</i> = .012) and neoplasm risk (<i>P</i> = .041). Lesion size, echogenicity, vascularity, multinodularity, lymphadenopathy, and solid areas on ultrasound were not significant in predicting malignancy or neoplasm (<i>P</i> > .05).ConclusionThe presence of oncocytes in thyroid aspirates does not increase malignancy risk. Most malignant oncocytic thyroid aspirates are not attributable to oncocytic carcinomas but papillary thyroid carcinomas. Ultrasound and thyroid function tests are helpful in the risk assessment of these cases.RelevanceFor treatment or follow-up decisions in patients with oncocytes in thyroid aspirates.