The incidence of cancer and rate of false-negative cytology in thyroid nodules greater than or equal to 4 cm in size.

BACKGROUND

High false-negative rates for fine needle aspiration biopsy (FNAB) of thyroid nodules greater than 3 cm have prompted recommendations for diagnostic lobectomy. We considered the presence of a greater than 4 cm nodule an independent indication for thyroidectomy regardless of FNAB results.

METHODS

We reviewed clinical data from 223 patients with thyroid nodules greater than or equal to 4 cm operated on from July 2003 to November 2006. Unifocal micropapillary cancer was considered clinically insignificant.

RESULTS

Clinically significant thyroid cancer was frequent, occurring in 57 of 223 patients (26%). Subgroup analysis showed that 43 of 223 patients (19.3%) had carcinoma within the mass and that 7 of 223 patients (3.1%) had significant carcinoma elsewhere in the resected thyroid. Multifocal micropapillary cancer was found in an additional 7 of 223 patients (3.1%). Preoperative FNAB was read incorrectly as benign in 9 of 71 patients with cancer (13%) (16% including multifocal micropapillary carcinoma). Benign FNAB results failed to identify 24 (34%) follicular lesions (including 7 cancers). In patients with preoperative FNAB results categorized as indeterminate lesions, 17 of 43 patients (40%) had carcinoma of the mass on final pathology.

CONCLUSIONS

In thyroid nodules greater than or equal to 4 cm, the incidence of carcinoma is high with a high false-negative rate for preoperative benign cytology. Thyroid nodules greater than or equal to 4 cm should be considered for diagnostic lobectomy regardless of FNAB results.