Clinical and histopathologial characteristics of papillary thyroid microcarcinoma (PTMC)
Elisabete Rodrigues1,2, Ana Sousa1, Luis Matos Lima1, Amadeu Pimenta1,2 & Jose Luis Medina1,2
Introduction: The recognition of thyroid microcarcinoma has been increasing in recent years probably as a result of the widespread use of ultrasound-guided fine-needle aspiration biopsies (FNAB) of small non palpable nodules and possibly of a more extensive histological examination.
Objectives: To describe clinical and histological characteristics of papillary thyroid microcarcinoma and compare them according to its size (< or ≥5 mm).
Methods: Retrospective analysis of clinical and pathological data of all patients operated on for thyroid cancer at our hospital between 2006 and 2008. Statistical analysis was done with SPSS 17.0 for Windows.
Results: During this period 533 patients (83 males, 450 females with a mean age of 54.5±14.0 and 51.8±14.7 years old, respectively) were diagnosed and treated for thyroid cancer at our institution. Of the 588 pathology reports evaluated in 370 there was a diagnosis of PTMC. Of these 172 were >5 mm (group A) and 198 <5 mm (group B). When comparing these groups according to gender, age at diagnosis (<45 or ≥45 years), coexistence of Hashimotos thyroiditis, mutifocality/multicentricity, capsular invasion, vascular invasion, extrathyroidal extension and lymph node involvement we found differences between them in terms of age at diagnosis (58 (55%) were <45 years in group A vs 107(43%) in group B; P=0.04) and lymph node metastasis (6 in group A (3,5%) vs 1 (0.5%) in group B; P<0.035). No distant metastasis was observed in this study.
Conclusions: PTMC is frequently found and the optimal treatment is still debatable. Some patients with PTMC have clinical and histopathogical poor prognostic factors, but in these series only tumors larger than 5 mm were significantly associated with lymph node metastasis. An interesting finding was the higher frequency of PTMC <5 mm in older patients. We can hypothesize that they reflect the indolent course of some of these tumors, that belong to the papillary family neoplasm, but are not necessarily malignant. Papillary microtumor was proposed in 2003 as a new term for a subset of PTMC, by a group of pathologists (Rosai J et al.).