Background: Fine needle aspiration biopsy (FNA) is the cornerstone of assessment of thyroid nodules. Cytological criteria for benign (THY2) and malignant (THY5) nodules are well-established and reliable. In a minority of patients cytology raises the possibility of a neoplasm (THY3) and only formal histological assesment can differentiate between benign and malignant lesions.
Method: Retrospective review of histological and clinical data in a cohort of patients with thyroid nodules with cytological diagnosis of follicular neoplasm (THY3).
Results: Between Jan 2000 and October 2006, out of a total of 2078 patients who underwent thyroid FNAs, there were 89 THY3 reports (approx 1:20). There were 19 men and 70 women, aged 1776 years. Thyroid lobectomy was performed in 82 patients and total thyroidectomy in 7 patients.
Histology demonstrated a thyroid carcinoma in 24 patients (15 follicular, 4 medullary, 3 papillary, 1 Hurthle cell and 1 poorly differentiated).
Benign changes were found in 65 patients (40 follicular adenomas, 10 Hurthle adenomas, 6 multinodular goitres, 4 adenomatoid nodules, 2 Hashimoto thyroiditis 1 colloid nodule).
Malignancy was more common in women (20/70 vs. 4/19, P<0.001 chi test) in younger patients (median age 31 vs. 50 yrs) and in larger nodules (median 31 mm vs. 28 mm).
Some 8/17 nodules over 40 mm in diameter were carcinomas, compared with only 12/53 in nodules under 40 mm (P<0.01, chi test).
Conclusion: Only one in four patients with cytological features of a follicular neoplasm has a thyroid carcinoma. A large nodule (>4 cm) in a young patient has a high likelihood of being a cancer and arguably such patients could be offered total thyroidectomy rather than diagnostic lobectomy.