Papillary microcarcinoma: is there any difference between clinically overt and occult tumors?

Papillary microcarcinoma (PMC) is a subtype of papillary thyroid carcinoma (PTC) associated with excellent prognosis. However, clinical and biologic behaviors of PMC may vary considerably between tumors that are clinically overt and those that are occult.

From 1964 to 2003, 185 of 628 patients with PTC were identified as having PMC, based on tumor size < or = 1 cm. There were 110 overt and 75 occult PMCs detected based on clinical presentation. The clinicopathologic features, treatment, and long-term outcome of PMCs were evaluated and compared between the two groups.

There were 37 men and 148 women with a median age of 45 years (range: 11-84 years). The median tumor size was 6.2 mm. Thirty-eight (21%) patients presented with cervical nodal metastases. Three (1.6%) had distant metastases and 5 (2.7%) underwent incomplete resection. Bilateral procedures were performed for 129 patients (70%) and 53 (29%) received postoperative I131 treatment. During a mean follow-up of 8.2 years, 4 patients died of the disease and 13 developed recurrence. Clinically overt PMCs were significantly larger, were more likely to be multifocal, and more likely to lead to bilateral thyroidectomy. Extrathyroidal or lymphovascular invasion, nodal metastases, I131 ablation, high-risk tumors, and postoperative recurrence occurred in overt PMC only. Patients with nodal metastases had a decreased survival and an increase in locoregional recurrence.

Despite a relatively good prognosis in PMC, a distinction should be made between clinically overt and occult PMCs in which clinically overt PMC should be managed according to tumor risk profile and clinical presentation.