Papillary thyroid carcinoma with an adenoid cystic pattern: report of a case with fine-needle aspiration cytology and immunocytochemistry

Although fine-needle aspiration (FNA) cytologic features of conventional papillary thyroid carcinoma (PTC) and some of its variants have been documented in the literature, PTC with an adenoid cystic pattern has not so far been described. A 35-year-old woman presented with solitary cold nodule in the right lobe of thyroid. FNA smears from the nodule showed features of PTC such as papilliform clusters, monolayered sheets, psammoma bodies, increased frequency of nuclear grooves, and intranuclear cytoplasmic inclusions. In addition, there were areas of follicular formation and light-pink to deep-purple hyaline globules with a laminated appearance and surrounded by neoplastic cells, reminiscent of adenoid cystic carcinoma. These globules were present in 53% of the follicles. Immunocytochemical staining for thyroglobulin yielded positive cytoplasmic reaction in the neoplastic cells. Histopathology of the thyroidectomy specimen confirmed the cytodiagnosis of PTC. The hyaline globules were present focally and were light pink to deep purple with a laminated appearance resembling psamomma bodies. The colloid and follicular cells were positive for thyroglobulin but the hyaline globules were negative. Von Kossa staining for calcium revealed positive reaction in the psamomma bodies and some of the hyaline globules, indicating that the globules may be the beginning of psammoma bodies. Thus, FNA cytology was useful in diagnosing an unusual variant of PTC.