Fine Needle Aspiration Cytology of Warthin-like Papillary Thyroid Carcinoma: A Brief Case Report

The Warthin-like variant of papillary thyroid carcinoma (WL-PTC) was first introduced by Apel et al. 1 in 1995 as an extremely rare subtype of papillary thyroid carcinoma (PTC) that is characterized by papillary architecture, lined by Hürthle cells, with classical cytologic features of PTC cells, and a heavy lymphocytic stroma of the papillary core. WL-PTC is now classified in the World Health Organization terminology as a special subtype of an oncocytic variant of PTC. 2 Its histopathological features have been relatively well documented in cases that followed the first 13 that were described by Apel et al. However, the cytologic features of WL-PTC in fine needle aspiration cytology (FNAC) are described rather poorly and by only a few authors. 3-6 Although Kim et al. 7 have documented the cytologic features of an oncocytic variant of PTC in a Korean patient, FNAC of WL-PTC has not been reported in Korea. FNAC is being used widely for initial diagnosis of thyroid lesions for a treatment plan decision. The first cytological picture of WL-PTC highly resembles that of benign lymphocyte-rich thyroid lesions such as Hashimoto's thyroiditis. Therefore, knowledge about key points in the differential cytological diagnosis is essential for an accurate diagnosis and appropriate treatment. Here, we present WL-PTC with FNAC for the first time in Korea in a teaching case involving liquid-based cytology (LBC) preparation in a 31-year-old woman. A 31-year-old Korean woman was referred to the department of surgery with a hypoechoic solid nodule in the upper pole of her left thyroid that was found during a routine health checkup (Fig. 1A). The nodule measured 0.99×0.75 cm and was accompanied by microcalcifications. The remaining thyroid pa-renchyma was hypoechoic and heterogeneous, which suggested Hashimoto's thyroiditis. Thyroid function tests, serum calcium, and parathyroid hormone level were within normal ranges. An aspiration of the mass was performed with a 21-gauge needle, and an air-dried smear was stained using the Papanicolaou (Pap) method. Another smear was fixed in 95% alcohol and stained with hematoxylin and eosin (H&E). The remaining aspirates were fixed in SurePath (BD Diagnostics-Tripath BD Bioscienc-es, Oxford, UK) liquid medium and processed according to LBC protocols. After the cytologic diagnosis was made, total thyroidectomy was performed (Fig. 1B). Cytology using conventional smears stained either by Pap or by H&E demonstrated relatively low cellularity with mainly isolated follicular cells and some small irregular clusters on a lymphocyte-rich background (Fig. 2). The follicular cells displayed …