Preoperative Cytologic Diagnosis of Warthin-like Variant of Papillary Thyroid Carcinoma

Abstract

Background: Warthin-like variant of papillary thyroid carcinoma (WLV-PTC) is a relatively rare variant of papillary thyroid carcinoma with favorable prognosis. However, preoperative diagnosis using fine-needle aspiration (FNA) specimens is challenging especially with lymphocytic thyroiditis characterized by Hürthle cells and lymphocytic background. To determine a helpful cytological differential point, we compared WLV-PTC FNA findings with conventional papillary thyroid carcinoma with lymphocytic thyroiditis (PTC-LT) and conventional papillary thyroid carcinoma without lymphocytic thyroiditis (PTC) regarding infiltrating inflammatory cells and their distribution. Preoperative diagnosis or potential for WLV-PTC will be helpful for surgeons to decide the scope of operation.

Methods: Of the 8,179 patients treated for papillary thyroid carcinoma between January 2007 and December 2012, 16 patients (0.2%) were pathologically confirmed as WLV-PTC and four cases were available for cytologic review. For comparison, we randomly selected six PTC-LT cases and five PTC cases during the same period. The number of intratumoral and background lymphocytes, histiocytes, neutrophils, and the presence of giant cells were evaluated and compared using conventional smear and ThinPrep preparations.

Results: WLV-PTC showed extensive lymphocytic smear with incorporation of thyroid follicular tumor cell clusters and frequent histiocytes. WLV-PTC was associated with higher intratumoral and background lymphocytes and histiocytes compared with PTC-LT or PTC. The difference was more distinct in liquid-based cytology.

Conclusions: The lymphocytic smear pattern and the number of inflammatory cells of WLV-PTC are different from those of PTC-LT or PTC and will be helpful for the differential diagnosis of WLV-PTC in preoperative FNA.

Keywords: Biopsy, fine-needle; Hashimoto disease; Thyroid cancer, papillary; Warthin-like variant.

Fig. 1.

Microscopic findings of Warthin-like variant of papillary thyroid carcinoma (WLV-PTC), conventional papillary thyroid carcinoma with lymphocytic thyroiditis (PTC-LT), and conventional papillary thyroid carcinoma without lymphocytic thyroiditis (PTC). (A) Histologic findings of WLV-PTC. WLV-PTC is composed of atypical follicular cells with abundant oxyphilic cytoplasm and nuclear grooves (inset) showing papillary structures with abundant lymphoid stroma. (B, C) Conventional smear of WLV-PTC showing irregular papillary clusters and numerous lymphocytes in tumor clusters in the bloody background. (D, E) Inflammatory and multinucleated giant cells are rather evenly distributed and hypercellular relative to the conventional smear. Intratumoral lymphocytes are easily seen. (F) Histologic findings of PTC-LT. (G, H) Conventional PTC-LT smear showing papillary tumor clusters without intratumoral lymphocytes, but some neutrophils seen around the tumor clusters in the lymphocytic background. (I, J) Peritumoral neutrophils seen in the lymphocytic background. (K) Histologic findings of PTC. (L–O) Hypercellular smear showing classic cytologic features of papillary carcinoma without inflammatory cells in background in both the conventional smear (L, M) and in ThinPrep (N, O) preparations.