[Non-incidental papillary microcarcinomas of the thyroid]

The clinical significance of papillary microcarcinoma of the thyroid gland keeps being controversial. Its high prevalence in autopsies and as incidental findings in thyroidectomy specimens for benign pathology indicate an indolent clinical behavior. Nevertheless some of the microcarcinomas develop lymph node metastasis and local recurrence. To determine the clinical and pathological characteristics of non-incidental papillary microcarcinomas of the thyroid (PTM -NI). 18 patients with diagnosis of non-incidental papillary microcarcinoma (tumor < or = 1 cm) with nodular expression in the thyroid gland or with lymph node metastasis have been studied. Initial diagnosis, prediction factors and evolution have been evaluated. Of 18 patients with PTM-NI, 12 demonstrated lymph node metastasis. 6 patients had positive fine needle aspiration (FNA) of palpable thyroid nodules. Multifocality and extraglandular extension were associated with lymph node metastasis. Seven of the nine metastatic lymph nodes diagnosed by FNA were cystic. Histologically 83.3% of the nodules in the thyroid were non-encapsulated and showed papillary growth pattern. Multifocality and extrathyroid infiltration were associated with lymph node metastasis at presentation. 46% of the patients with thyroid nodules > or = 4 mm and lymph node involvement (N1) showed recurrence/persistence. The non-incidental intrathyroideal papillary microcarcinoma without capsular involvement, extraglandular extension or lymph node metastasis (N0) did not demonstrate recurrence. These results suggest two groups of non- incidental papillary microcarcinoma of the thyroid (PMT-NI), one intraglandular without risk of evolution -N0- and other extraglandular at risk of recurrence -N1-.