Cytomorphologic features as predictors of aggressiveness in patients with pT1 papillary thyroid carcinoma: a retrospective study of associations with clinicopathological parameters in 226 fine-needle aspirates

Background Distinguishing aggressive pT1 papillary thyroid carcinomas (PTCs) from indolent PTCs before or during surgery is important. To the best of our knowledge, few reports in the literature have examined the value of the cytomorphologic features of PTC as predictors of aggressiveness. Methods This retrospective study included 226 pT1 PTC patients who underwent preoperative fine-needle aspiration cytology (FNAC) and surgery at Peking University Cancer Hospital between January 2018 and December 2019. Data on the clinical characteristics and pathological results were obtained from the electronic medical record database. All FNAC smears were blindly reviewed by two independent cytopathologists, and the associations between nine cytomorphologic features (lymphocytes, multinucleated giant cells, cellularity, cellular adhesiveness, nuclear size, nuclear pleomorphism, nuclear membrane regularity, intranuclear pseudoinclusions and the amount of cytoplasm) and clinicopathological parameters were statistically analyzed. Results Univariate analysis showed that cellularity, intranuclear pseudoinclusions, cellular adhesiveness, nuclear size, and nuclear pleomorphism were strong predictors of some clinicopathological parameters such as extracapsular invasion (ECI) and lymph node metastasis (LNM). Multivariate analysis confirmed that cellular adhesiveness was a strong independent predictor of ECI (P=0.001) and LNM (P<0.001), and the amount of cytoplasm can also predict LNM (P=0.024). Conclusions Cytomorphologic features including cellular adhesiveness and the amount of cytoplasm in preoperative FNAC smears could be a valuable tool for predicting ECI or LNM and may be predictors of aggressiveness in patients with pT1 PTC.