Fine-needle aspiration cytomorphology of papillary thyroid carcinoma with NTRK gene rearrangement from a case series with predominantly indeterminate cytology.

Our study demonstrates that most cases of NTRK rearrangement lack classic PTC cytomorphologic characteristics. Loosely cohesive groups and single cells with granular, sometimes vacuolated cytoplasm and subtle nuclear features are often seen on FNA specimens. Recognizing these characteristics may be helpful to preoperatively prompt molecular testing, including NTRK rearrangement analysis.