Cystic Papillary Thyroid Carcinoma

Cystic change is commonly seen in papillary thyroid carcinoma. Macrophages can be seen in variable numbers with or without hemosiderin-laden pigments. Some cytologic features have been found to be useful in the differential diagnosis between cystic papillary thyroid carcinoma and cystic degeneration in a benign goiter. Atypical histiocytoid cells have been described in smears of cystic papillary thyroid carcinoma. These atypical histiocytoid cells have abundant vacuolated cytoplasm, nuclear pleomorphism, and nucleoli. They are larger and more atypical than benign histiocytes. The combination of macrophages, hemosiderin, cellular debris, and old blood in the background may obscure distinction between cystic papillary thyroid carcinoma and cystic goiters. Ancillary immunohistochemical markers and mutational analysis may be useful in challenging specimens.