Fine needle aspiration cytology of medullary thyroid carcinoma: a review of 18 cases.

A series of 18 consecutive medullary thyroid carcinomas (MTC) diagnosed by fine needle aspiration cytology (FNAC) is described. The most important diagnostic cytologic criteria were the dispersed cell pattern, the polygonal appearance of the cells, binucleated cells and the presence of amyloid. Other less common cytologic features are reported and the variable microscopic appearance of MTC is pointed out. The possibility that this cytologic variability of MTC may be by itself an important diagnostic feature is proposed.