Should Atypical Follicular Cells in Thyroid Fine-Needle Aspirates Be Subclassified?

BACKGROUND: Recently reported Bethesda terminology suggests the use of the term atypical follicular cells for thyroid fine-needle aspirates. Previous work has suggested that some types of atypical follicular cells have different risks of malignancy. METHODS: The author reviewed the results of all thyroid aspirations with surgical resection performed during the past 13 years at our institution, subclassified the atypical follicular cells, and compared their relative risk of malignancy. RESULTS: During the 13 years in question a total of 7089 cases were aspirated with 1331 resections. A total of 548 (14%) of all cases were classified as atypical follicular cells, and 204 (37%) were resected with an overall risk of malignancy of 25%. The risk of malignancy for atypical follicular cells subclassified as rule out papillary carcinoma was significantly higher (38%) than the other atypical cells. The risk of rule out Hurthle cell neoplasm was, at 7%, significantly lower than the other cases of atypical follicular cells (P<.001 and P<.02, respectively). CONCLUSIONS: Different types of atypical follicular cells have significantly different risks of malignancy. This disparity of risk should be communicated by the cytologist. Cancer (Cancer Cytopathol) 2010;118:186-9. (C) 2010 American Cancer Society