WARTHIN‐LIKE TUMOUR OF THE THYROID — THE FINE NEEDLE ASPIRATION CYTOLOGY FEATURES

Dear Editor Warthin-like tumour (WLT) is a newly described variant of papillary thyroid carcinoma (PTC). We report one such case which was studied both by ®ne needle aspiration cytology (FNAC) and histopathology. A 50-year-old lady presented with thyroid swelling of 7 years duration, with recent onset of pain. The swelling was con®ned to the left lobe. Thyroid function test was indicative of euthyroid state. Fine needle aspiration yielded high cellularity consisting of epithelial cells admixed with lymphoplasmacytoid cells. The epithelial cells were arranged singly, in monolayered sheets and in three-dimensional papillary clusters with ®brovascular core (Figure 1). The cytoplasm was abundant and varied from amphophilic to eosinophilic granular in nature. Nuclear grooves and intranuclear cytoplasmic inclusions were evident (Figure 2). Also seen were small discohesive groups of Hurthle cells with hyperchromatic nuclei and rows of columnar cells with eosinophilic cytoplasm. Associated features were the presence of siderophages and large multinucleated giant cells, some with foamy cyanophilic cytoplasm and others with pink wavy cytoplasm without phagocytic material. A diagnosis of PTC with lymphocytic thyroiditis was suggested. A total thyroidectomy was done. The left lobe of the thyroid had an unencapsulated tumour measuring 3 cm in its largest dimension with a granular grey white cut surface. Histopathology showed features of Warthinlike tumour (Figure 3). FNAC features of WLT of thyroid have recently been documented. Epithelial cells with combined features of PTC and Hurthle cells arranged in three-dimensional clusters with intermingling lymphoplasmacytoid cells suggest a diagnosis of WLT. Lesions of the thyroid gland which show an admixture of epithelial cells and chronic in ̄ammatory cells include the tall cell variant (TCV) and di€use sclerosing variant (DSV) of PTC. Hashimoto's thyroiditis (HT) and primary thyroid lymphomas also have to be considered in the di€erential diagnosis. TCV±PTC is often associated with intense chronic in ̄ammation and on FNA it may not be possible to distinguish it from WLT. The number of tall cells (height more than twice the width) required to qualify for a cytologic diagnosis of TCV±PTC is reported to range from 5% to 60% (mean 46%). DSV±PTC shows scattered squamous elements and a polymorphous lymphomonocytic background, together with features of papillary carcinoma. This tumour requires more extensive surgery and distinction between these two lesions on FNAC is hence, essential. In HT, ̄at cell sheets, thin cell clusters and only a few isolated cells are seen, unlike the three-dimensional tissue fragments with loosely cohesive cells and a large number of isolated single cells seen in a neoplastic lesion. Mixed Hurthle cell and hyperplastic features seen within individual cells suggest HT. When HT is associated with PTC the distinctive nuclear features give a clue to the diagnosis. The lymphoid cells in HT appear reactive and polymorphic. Activated lymphoid cells such as immunoblasts are generally not observed in WLT. In lymphomas the monotony of lymphoid cells and lack of nuclear features of PTC in the epithelial cells permit di€erentiation from WLT. In conclusion WLT of thyroid has distinctive cytological features. With increasing experience an accurate diagnosis is possible. The clinical course and prognosis of this tumour, although not clearly understood, is