Clinicopathologic Differences Between Micropapillary and Papillary Thyroid Carcinoma

The aim of this study is observing the clinicopathologic features of thyroid papillary microcarcinomas (PTMs) and comparing these features with papillary thyroid carcinoma (PTC).

A total of 86 surgically treated patients suffering from PTC were evaluated retrospectively. Group 1 (G1) included patients with a tumor <1 cm, while Group 2 (G2) included patients with a tumor >1 cm. The two groups were compared in terms of the preoperative thyroid-stimulating hormone (TSH) level, anti-thyroid peroxidase antibody (anti-TPO) and antithyroglobulin antibody (TgAb) values, multicentricity, the lymphovascular invasion rate, the presence of extrathyroidal extension, and central and/or lateral lymph node metastasis.

There was no statistically significant difference observed between the groups in terms of the preoperative TSH level, anti-TPO, and TgAb values. The rate of multicentricity of the tumor in G2 was 66%, while it was 36% in G1 (p<0.001). The lymphovascular invasion rate in G1 was 14.2%, while it was 61% in G2 (p<0.001). The extrathyroidal extension rate of the tumor cells in G1 was 21.4%, while it was 63.6% in G2 (p<0.001). The central lymph node metastasis rate in G2 was 38.6%, while it was 4.8% in G1 (p<0.001). The lateral lymph node metastasis rate in G2 was 20.5%, while it was 0% in G1 (p<0.001).

PTMs are generally associated with good prognostic factors with high survival rates. However, the risk factors such as multifocality, extrathyroidal extension, and lymphovascular invasion increasing the recurrence risk are not rare in PTM. Thus, the patients having these histopathological features of the tumor should be followed more carefully.