Clinical Predictors of Minimal Extrathyroid Invasion of Papillary Thyroid Cancer
Authors: Lishchynskyi Pavlo , Palamarchuk Volodymyr , Kuts Volodymyr , Mazur Oleh , Zemskov Sergii , Tovkai Oleksandr , Dronov Olexii 
Published: July 2022

extrathyroidal invasion (ETI) of papillary thyroid cancer (PTC) is a risk factor for lo-coregional metastasis. The clinical significance of minimal ETI depending on the primary tumor size
has not been studied thoroughly. The combination of tumor diameter and minimal ETI can be used asa reliable prognostic factor for persistence of the disease. Given that the identification of the minimal
ETI is possible only during the final histopathological study, there is a need to assess the existing pre-operative clinical predictors that increase the probability of minimal ETI of PTC. The aim of the study
is to assess preoperative clinical predictors that increase the probability of minimal extrathyroidalinvasion of papillary thyroid cancer. A retro-prospective single-center study of preoperative clinicalpredictors that increase the probability of extrathyroidal invasion of thyroid cancer was conducted.Data from 514 patients aged 5 to 81 years were processed. Patients underwent surgery for papillarythyroid cancer for the first time. Scope of the operation: extrafascial thyroidectomy. Central neckdissection. Lymphadenectomy. All patients had clinical signs of low risk of recurrence. The meanage of patients was 44.4 ± 14.5 years. There were 91 men (17.7%) and 423 women (82.3%). Patientswere divided into two groups: group 1 with 169 patients with minimal extraorganic invasion aged 5to 71 years, group 2 with 345 patients without invasion aged 10 to 81 years. The following featureswere taken into account for the analysis: 1) age of patients; 2) their sex; 3) the size of the dominanttumor. The results were statistically processed using a specialized statistical program StatPlus Prov.7 (AnalystSoft Inc.) and Epitools statistical calculators (Ausvet, https://epitools.ausvet.com.au/).According to the results, both by age (mean age of patients in group 1 - 44.7 ± 14.4 years; meanage of patients in group 2 - 44.3 ± 14.6 years) and by sex (in group 1 – 30 men (17.8%), 139 women
(82.2%), in group 2 – 61 men (17.7%), 284 women (82.3%), the groups were almost identical, bothgroups were significantly (p <0.01) dominated by women. The size of the primary tumor in group1 - 15.0 (10.0; 20.0) mm - was statistically significantly higher (p <0.001) than in the second - 10.0(7.0; 15.0) mm. Most of patients (71.0%) with invasion had a primary tumor size > 10 mm, while ingroup 2 there were only 42.6% of such patients. Within the size ranges up to 10 mm, the probabilityof detection of invasion is 14.0% - 21.6%, while within the size ranges over 10 mm, it may be 41.9% -50.0%. A tumor size of PTC over 10 mm, with a diagnostic strength of 61.9%, increases the risk ofminimal extrathyroidal invasion. The average size of the primary tumor in the group of patients withminimal ETI is 15.0 (10.0; 20.0) mm, which is statistically significantly higher (p <0.001) than thesame value in the group of patients without EIT - 10.0 (7.0; 15.0) mm. In patients with a PTC tumor
size of less than 10 mm, the probability of minimal ETI ranges from 14.0% to 21.6%, while the prob-ability of minimal ETI in patients with a tumor size over 10 mm ranges from 41.9% to 50.0%. Given
that minimal ETI may be one of the factors of increased risk of PTC locoregional metastasis, surgeryfor PTC patients with a tumor size over 10 mm should be supplemented with central neck dissection,lymphadenectomy. A tumor size of PTC over 10 mm, with a diagnostic strength of 61.9%, increases the risk of minimal extrathyroidal invasion, which is also an argument in favor of central neck dis-section, lymphadenectomy during surgery for patients with tumor size over 10 mm. The patients’ age and sex cannot be the factors that increase the risk of minimal extrathyroidal invasion of papillarythyroid cancer.