Follicular and Hürthle cell lesions of the thyroid: can inconclusive results be minimized?

To assess the cytologic criteria for distinguishing neoplastic from nonneoplastic follicular cell and Hürthle cell thyroid lesions.

Ten previously described and commonly used cytologic criteria were evaluated and graded on a 0-4 scale in a consecutive series of thyroid fine needle aspirations (FNAs) reported as follicular or Hürthle cell neoplasms or lesions. Scoring was compared to subsequent surgical outcome.

A total of 93 (57fo llicular cell and 36 Hühle cell) cases was analyzed. No individual cytologic feature was helpful in distinguishing benign neoplarms from malignancy in either category (p > 0.05), but 4 or more coexistent cytologic features in combination were identified in 50.0% of follicular neoplasms, 13.6% of Hürthle cell neoplasms and none of the nonneoplastic lesions. An unexpected number (13 of 93, 14.0%) of unrecognized papillary carcinomas, some of follicular subtype, was encountered.

In this series, the indeterminate thyroid FNA category could have been reduced by diagnosis of samples with 4 or more of the studied criteria as definite follicular (50% of cases) or Hürthle cell (13.6% of cases) neoplasms and by more astute recognition of papillary carcinomas (14.0% of cases), which blend into this category, often as a result of less-than-optimal sampling or preservation.