Anaplastic Thyroid Carcinoma: Cytomorphologic Features on Fine-needle Aspiration and Associated Diagnostic Challenges

Peter Podany, MD; Rita Abi-Raad, MD; Andrea Barbieri, MD; James Garritano; Manju L. Prasad, MD; Guoping Cai, MD; Adebowale J. Adeniran, MD; Syed M. Gilani, MD


Am J Clin Pathol. 2022;157(4):608-619. 

In This Article

Abstract and Introduction


Objectives: Anaplastic thyroid carcinoma (ATC) is an aggressive malignancy, and early diagnosis, often aided by fine-needle aspiration (FNA), is key to improving patient prognosis. While the current literature describes some of the cytologic features (CFs) of this entity, a comprehensive examination of the CFs has not yet been performed.

Methods: We retrospectively searched our electronic database for ATC cases with available slides between January 2008 and December 2019. Cases were examined for 22 CFs and compared with a control group of differentiated thyroid carcinoma.

Results: A total of 18 ATC cases meeting our inclusion criteria were identified. Most cases showed moderate to high cellularity (83%) and epithelioid cytomorphology (83%). Architecture included either predominantly groups/clusters of tumor cells (56%) or single tumor cells (44%). The other CFs were as follows: nuclear enlargement (100%), nuclear crowding (89%), nuclear membrane irregularities (100%), multinucleated tumor cells (33%), and background acute inflammatory cells (50%). Of the CFs examined, statistically significant differences between ATC and the control groups were found in the following: nuclear pleomorphism, coarse/clumped chromatin, macronucleoli, apoptosis, and necrosis.

Conclusions: Identification of key CFs in FNA coupled with the clinical history aids in the diagnosis of ATC and helps distinguish it from other mimickers.


Anaplastic thyroid carcinoma (ATC) is one of the most aggressive thyroid malignancies and is associated with low overall survival rates.[1] It typically presents as a rapidly enlarging thyroid mass most often affecting patients during the sixth and seventh decades of life.[2] ATC can either arise de novo or in a background of differentiated thyroid carcinoma (DTC), typically papillary thyroid carcinoma (PTC). It is essential to appropriately evaluate and diagnose these cases in a timely manner, as patients with ATC with smaller tumor size (<5 cm) and without any nodal disease have better median survival rates compared with patients with larger tumor size (>5 cm) or disease metastatic to the lymph nodes.[3] Fine-needle aspiration (FNA) cytology plays an important role in the assessment and diagnosis of thyroid lesions, including ATC.[4] Some of the cytologic features of ATC have been described in previously published studies, but a comprehensive evaluation of cytologic features has yet to be performed.[5,6] The cytologic features evaluated in this study are more comprehensive than those reported in previous studies.