Encapsulated papillary thyroid carcinoma: is it a distinctive clinical entity with low-grade malignancy?

Encapsulated papillary thyroid carcinoma (EPTC) is commonly retained as a tumor with indolent clinical courses. Herein we focused on the search for factors predicting biological behavior and influencing prognosis of EPTC in comparison with the non-encapsulated counterpart of papillary thyroid carcinoma (NEPTC).

From January 1998 to May 2009, 348 patients underwent thyroidectomy in our surgical department because of papillary thyroid carcinoma (PTC). A cross-sectional study of 52 patients with EPTC and 296 patients with NEPTC was carried out: demographic data, tumor characteristics, diagnostic results, patient management, post-operative and follow-up results were evaluated.

EPTC patients were significantly younger than patients with NEPTC (44.5 vs 48.8 yr, p<0.04). Mean tumor size was significantly greater for EPTC than for NEPTC (2.36 vs 1.41 cm, p<0.001). Tumor multifocality, thyroid capsular invasion, and lymph node involvement at diagnosis were significantly associated with NEPTC (p=0.0001, p<0.0001, and p=0.027, respectively). Multivariate analyses showed that NEPTC classical variant were at risk for both thyroid capsular invasion and nodal involvement (odds ratio 6.870 and 9.514, respectively) while EPTC were not. Nodal metastasis at diagnosis was the only factor influencing recurrence.

The majority of EPTC had risk-free clinical courses as a result of their low risk of locoregional spread. However, definitive recommendations need a longer follow-up and a comparison with a lesser treated group of patients belonging to the same category of risk at diagnosis.