Article Title: Features of Anaplastic Thyroid Carcinoma on Liquid-based Cytology and Pitfalls in the Cytologic Diagnosis of Thyroid Tumors with Spindle Cells: A Case Report
Author: Ji Young Kim*, Songmi Noh, Eunah Shin, Jeong Yun Shim
Published Date: February 20, 2018
Anaplastic thyroid carcinoma (ATC) is a highly aggressive but rare thyroid malignancy. Cytologically it typically shows a mixture of three cell groups, i.e. spindle cells, giant cells, and squamoid/epithelioid cells. But, when it is composed predominantly of spindle cells, the diagnosis of ATC may not be robust. Here we report a case of thyroid anaplastic carcinoma predominantly composed of spindle cells with its cytologic features on liquid-based preparation. A 61-year old male visited our hospital with a 7cm-sized thyroid nodule detected on a regular checkup. The initial fine needle aspiration was unsuccessful showing only cystic fluid. The patient underwent radiofrequency ablation (RFA) with decrease in the size of the mass that, after six month, enlarged back again. Left lobectomy and isthmusectomy was performed. Liquid-based cytologic sample was prepared using the scraped material from the resected mass. Cytologically, the predominant cells were spindle cells, arranged in clusters or in single cells. They had enlarged nuclei with vesicular chromatin with minimal chromatic clumping. The nucleoli were small but prominent. Giant cells, squamoid cells, or large pleomorphic cells were not present. The background was slightly necrotic and degenerative. When a thyroid FNA from a thyroid nodule reveals spindle cells, differential diagnosis should include ATC, medullary carcinoma, other sarcomas, reactive fibrosis in Riedel’s thyroiditis, etc. The degree of cytologic atypia of the spindle cells, the presence of other components such as giant cells and squamoid/epithelioid cells, along with the immunohistochemical staining for calcitonin, CEA, PAX-8, and/or TTF-1 can readily differentiate ATC from others.