Diagnostic relevance of fine needle aspiration cytology for follicular lesions of the thyroid: retrospective study.

AIM To determine diagnostic relevance of cytologic subclassification of follicular lesions of the thyroid and its role in the therapeutic approach. METHODS We performed a retrospective analysis of the data of patients who underwent thyroid surgery at the Sisters of Mercy University Hospital, Zagreb, between March 1995 and February 2001, and had a report of preoperative fine needle aspiration (FNA) biopsy of thyroid follicular lesion, which comprises cellular follicular lesion, suspicious for follicular neoplasm, or follicular neoplasm. RESULTS Out of 110 patients with preoperative FNA biopsy diagnosis of follicular lesion, 86 (78%) had a lesion corresponding histologically to a neoplasm. However, a malignant tumor was found in only 6% of the patients. In the diagnostic categories of cellular follicular lesion and lesion suspicious for follicular neoplasm, the rate of malignancy was even lower, 3% and 4%, respectively. We found significant difference between FNA and histologic findings in distinguishing non-neoplastic from neoplastic thyroid lesions in the category of cellular follicular lesion and follicular neoplasm. CONCLUSION Due to the low malignancy rate in patients with FNA biopsy diagnoses of cellular follicular lesion or lesion suspicious for follicular neoplasm of the thyroid, we suggest close clinical follow-up of such patients, rather than immediate surgical intervention.