Histologic Outcome of Indeterminate Thyroid Nodules Classified at Low or High Risk

The revised Italian consensus for the classification and reporting of thyroid cytology (ICCRTC) was published in 2014. Very recently, a high reliability of ICCRTC in classifying low and high risk indeterminate nodules (Tir 3A and Tir 3B, respectively) was demonstrated. This finding prompted us to review our case series of thyroid indeterminate lesions to verify these data. Only lesions undergone FNAC from December 2014 to October 2017 with subsequent histology at our institutions were eligible for the study. All cytologic samples had originally been classified according to ICCRTC in the subcategories of indeterminate lesion, such as Tir 3A and Tir 3B by three cytopathologists and another one with more than 10 years experience, when necessary. Sixty-three indeterminate FNAC were diagnosed during the study period, of which 51 were subsequently surgically treated. Overall, 9 carcinomas (7 follicular and 2 papillary) and 42 benign lesions were found at histology. The cancer rate observed in the Tir 3A category (3/40, 7.5%) was significantly (p = 0.0015) lower than that found in Tir 3B (6/11, 54.5%). No significant differences were found in age and size of the sampled nodules between the two subcategories. We can confirm in our series that the Italian reporting system for thyroid cytology shows high reliability in discriminating low risk indeterminate lesions from those at high risk of malignancy.