S. C. Pawar1, R. S. Chamberlain1 1Saint Barnabas Medical Center,Surgery,Livingston, NJ, USA
Introduction: Papillary thyroid microcarcinoma (PTMC) usually follows an indolent course and is considered a low risk tumor. However recent studies have identified several cases of PTMC with locoregional recurrences in the neck and with distant metastases. It is imperative that the clinicians have a better understanding of PTMC and specifically characteristics of PTMC with aggressive behavior.
Methods: The Surveillance, Epidemiology, and End Results (SEER) program was queried for patients diagnosed with PTMC between 1989 and 2011. Age, gender, tumor size, lesion type, extent of disease, stage, surgery, and mortality were analyzed for papillary thyroid micro carcinomas (≤ 1cm) and compared to papillary tumors of size (> 1 cm). Clinical and pathological characteristics of patients with PTMC were compared to PTMC patients who died of cancer specific death using multivariate analyses.
Results:Among 53,429 patients diagnosed with Papillary thyroid carcinoma, 36,093(67%) were diagnosed with PTC tumors of size (> 1 cm) and 17,336 (32%) were PTMC (≤ 1 cm). The median age of the entire cohort was 48 yr (PTMC (49 yr) and PTC (48 yr)), however patients with PTMC with aggressive behavior were significantly old (64 yr). Females dominated the study cohort for both PTC (> 1 cm) and PTMC (≤ 1 cm) (73% vs 81% respectively). PTMCs were more likely to present as multifocal tumors compared to PTC (> 1 cm) (14% Vs 8% respectively). 82% of PTMCs had localized disease at the time of diagnosis, 17% had regional spread, and 1% had distant metastasis. Multivariate analysis identified extrathyroidal invasion, multifocality, male gender, Asian race, and tumors with regional and distant metastasis at diagnosis as significant independent predictors of mortality in PTMC patients. Patients with PTMC who died were more male (Odds ratio [OR], 4.34; p < 0.0001), of Asian ethnicity (OR, 1.35; p < 0.005), and elderly (OR, 9.77; p < 0.001).
Conclusion:Although most PTMCs are considered low risk, up to 17% of patients with PTMC exhibit aggressive behavior in regards to extrathyroidal invasion, multifocality, regional spread, distant metastasis at diagnosis, and may benefit from a more radical therapeutic approach. PTMCs with aggressive behavior are more common among male gender, elderly age group, and Asian ethnicity.
