Thyroid tumors: cytomorphology of follicular neoplasms.

From 2,012 fine-needle aspirations (FNA), performed by us between the years 1984 and 1988, we present a detailed cytomorphologic analysis of 95 cases that were diagnosed as neoplastic on histology and/or cytology and those that received an equivocal cytodiagnosis. Discussed are 37 lesions that have been diagnosed on cytology and/or histopathology as follicular neoplasms. In this group, there were 22 cases of histologically proven follicular carcinoma and 11 follicular adenomas. Three cases of multinodular goiter and one case of Hashimoto's thyroiditis with marked follicular hyperplasia have also been included because they received either a neoplastic or an equivocal cytodiagnosis. Of 22 follicular carcinomas, 12 were diagnosed on FNA as follicular neoplasms, eight as follicular carcinoma, one was a false-negative benign cytodiagnosis, and one was equivocal. Of 11 follicular adenomas, seven were diagnosed as follicular neoplasms and four were cytologically equivocal. Three cases of multinodular goiter and one Hashimoto's thyroiditis had been diagnosed on FNA as either follicular neoplasm or equivocal.