Background: Micropapillary Thyroid Cancer (MPTC) is defined as papillary thyroid cancer measuring less than one centimeter in size. Although there have been many studies involving MPTC, there is still a gap in the understanding of the behavior of MPTC in the Filipino population.

Objectives: This study aims to determine risk factors and prevalence of locoregional and distant metastasis upon diagnosis and the risk factors for persistent disease after thyroidectomy among patients with MPTC.

Methods: : This is a retrospective study that included all patients with histopathology result of MPTC from January 1, 2004 to December 31, 2012. Patients who had accompanying well differentiated thyroid tumors other than MPTC and those patients with a diagnosis of MPTC with no follow up after the surgery were excluded.

Results: A total of 109 patients were eligible for the study. The mean age was 46.06 years with majority being female (96.3%). The average tumor size was 0.502 cm. Seventy-five (68.81%) received Radioactive Iodine Therapy (RAI) after thyroidectomy. Nineteen patients (17.92%) had multifocal disease while 11 (10.09%) had multicentric disease. Fifteen patients (13.76%) had locoregional metastasis while eight (7.34%) had distant metastasis on diagnosis. Out of the 91 patients included for analysis of persistent disease, eight patients (8.79%) had persistent disease. Exact logistic regression showed that locoregional metastasis (p=0.0044) is a risk factor for distant metastasis at diagnosis. Age, sex, tumor size, multifocality, multicentricity, RAI, and extent of surgery did not reach statistical significance as independent risk factor for locoregional, distant metastasis on diagnosis, and persistent disease.

Conclusion: Although MPTC is considered an indolent type of well differentiated thyroid cancer, there are certain patients who may present with metastasis at diagnosis. Our data showed that locoregional metastasis is a risk factor for distant metastasis on diagnosis in patients having MPTC.

Keywords: Risk Factors, Metastasis, Micropapillary Thyroid Cancer

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