Assessment of risk factors in metastatic/recurrent tall cell variant of papillary thyroid carcinoma.

INTRODUCTION: Papillary thyroid carcinoma (PTC) is the most common malignant thyroid tumor. A great majority of the cases live a disease-free life with quite favorable prognosis. There are lots of variants of PTC and a few of them exhibit aggressive behaviour. Typical example is the tall cell variant (TCV). Patients experience a greater incidence of recurrence, nodal and extranodal metastases, tumor associated mortality than other variants of PTC. Studies related to TCV almost always compared it with its patient population of PTC according to risk factors and clinicopathologic features. The aim of this study is to evaluate the risk factors in metastatic/recurrent TCV.

MATERIALS AND METHODS: This is a retrospective cohort study of 1813 patients with differentiated thyroid carcinoma treated with radioiodine between 1992 and 2011. 56 of these patients are TCV. 34 of them developed metastasis/recurrence and 22 lived a disease-free life during the 23-year follow-up. We evaluated the risk factors in these metastatic and nonmetastatic subgroups.

RESULTS: We found tumor size, preablation thyroglobulin level, vascular invasion, preablation central and lateral cervical lymph node metastasis, preablation lung metastasis and stage independent risk factors. However age, preablation thyroglobulin level and stage appeared together as striking factors impacting metastasis in multivariate analysis.

CONCLUSION: Higher ablation doses up to 250-300 mCi should be administered to TCV patients having advanced stage (III,IV), pretty high preablation thyroglobulin level (over 400 ng/ml) and older age (over 52 years) especially with large tumor size (over 3.5 cm) and initial cervical lymph node metastasis.