*3.1. Patient Characteristics and Clinical Histopathological Features*

The patient characteristics and clinical histopathological features of the retrospective study cohort are summarized in Table 1. The median patient age at initial diagnosis was 50 years. (range 16–89) for the subgroup of benign nodules, 55 years. (range 25–80) for NIFTPs, 49 years. (range 19–78) for the invasive EFVPTCs and 52 years. (range 23–75) for the LT subgroup. The majority of patients were females (131, 79%) compared to male's patients (34, 21%). Clinical, radiologic, or pathologic follow-up data were also reviewed. The median duration of follow-up for the benign subgroup was 6.99 years., NIFTPs 4.10 years., invasive EFVPTC 3.26 years. and LT subgroup 4.13 years. No recurrence for malignant cases was found.

**Table 1.** Demographics and clinicopathologic features of the patient cohort.


\* Advanced thyroiditis was separated from other noninvasive categories due to co-existing significant lymphocytes/Hashimoto's thyroiditis. \*\* Average of tumor size was calculated from 27 cases out of 42 benign patients because the information of the remaining 13 cases was not available.

> According to the clinical histopathological features, all patients were allocated into four study subgroups- 42 benign nodules (25%), 41 NIFTPs (25%), 45 invasive EFVPTCs (27%) and 37 cases (22%) of encapsulated FVPTC lesions with coexisting significant lymphocytic thyroiditis and no capsular or vascular invasion (LT).
