Papillary thyroid microcarcinoma: incidence and prognostic factors.

The objective of this study was to define the prognostic factors of papillary microcarcinoma of the thyroid (PMCT), and to analyse their epidemiologic and histopathologic characteristics. Our series included 57 patients diagnosed with PMCT between 1994 and 2003 among 944 patients who underwent thyroid surgery. All the surgical specimens were examined in the same department of pathology using the same technique. The prognostic factors were elaborated from the results of the histological examination. The epidemiological and histopathological characteristics were also evaluated. Two sub-groups were distinguished: patients with node disease and/or with metastasis (17 patients) and patients without node disease and metastasis (40 patients). The architecture of PMCT was papillary in 14% of cases, follicular in 35% of cases and mixed in 49% of cases, with no significant difference between any two groups. Histopathologic characteristics such as the vascular extension, infiltration into the adjacent parenchyma or in the thyroid capsule are all indicative of a poor prognosis. Two categories of PMCT, with and without the risk of metastatic spread, can be identified from these prognostic factors.