Lymph node metastasis in thyroid papillary microcarcinoma: a study of 170 patients.

Objective: Papillary microcarcinoma of the thyroid has been described as either a normal variant or a serious malignancy. We describe our experience with papillary microcarcinoma and lymph node metastases.

Method: A total of 685 consecutive total thyroidectomies with central compartment neck dissection were reviewed for papillary microcarcinoma. Association of central compartment lymph node metastases with age, gender, tumour multifocality, bilaterality and extrathyroidal extension was analysed.

Results: Out of 170 papillary microcarcinoma cases, multifocality was found in 72 (42.4 per cent), bilaterality in 49 (28.8 per cent) and extrathyroidal extension in 16 (9.4 per cent). In all, 23 patients (13.5 per cent) had lymph node metastases. There was a significant association (p < 0.05) between extrathyroidal extension (but no other tumour characteristics) and lymph node metastases.

Conclusion: In all, 13.5 per cent of papillary microcarcinomas in our series showed lymph node metastases. Lymph node metastases were associated with extrathyroidal invasion of the papillary microcarcinoma.