The prevalence of thyroid cancer has witnessed a significant surge worldwide in recent decades, coinciding with the widespread adoption of medical check-ups [[1], [2], [3]]. While most thyroid cancers have a favorable prognosis [[4], [5], [6], [7]], advanced age is a significant risk factor associated with poorer outcomes. Although patients of advanced age generally face more challenging prognoses [[8], [9], [10], [11], [12], [13], [14]], the specific correlation between histological subtypes and this patient demographic remains under-investigated. [[15], [16], [17], [18], [19]]. Therefore, further investigation into clinicopathological factors and prognostic markers is essential, particularly within the elderly population.

Among non-anaplastic follicular cell-derived carcinomas, two distinct subtypes with intermediate prognoses have been identified: poorly differentiated thyroid carcinoma (PDTC) and differentiated high-grade thyroid carcinoma (DHGTC) [17,18,[20], [21], [22], [23]]. Both subtypes are defined as invasive high-grade carcinomas lacking anaplastic features, but they differ in their diagnostic criteria. PDTC is characterized by solid, trabecular, or insular growth patterns, convoluted nuclei, more than three mitoses per 2 mm2, and tumor necrosis [[24], [25], [26]]. DHGTC, while retaining some features of well-differentiated carcinomas, is defined by the presence of tumor necrosis and a mitotic rate of five or more per 2 mm2 [20,21,27]. The recognition of PDTC and DHGTC has refined the classification of thyroid carcinomas, highlighting entities with an intermediate prognosis that bridge the gap between well-differentiated and anaplastic carcinomas [28].

Telomerase reverse transcriptase (TERT), a key regulator of telomerase activity, plays a significant role in the pathogenesis of thyroid cancer [[29], [30], [31]]. TERT promoter mutations, found in a small percentage of well-differentiated carcinoma cases, enhance TERT gene expression and contribute to immortalization through telomerase activation [32]. TERT promoter mutations are often associated with clinicopathological factors such as advanced patient age, large tumor size, and extensive local infiltration, which are linked to worse clinical outcomes such as radioiodine refractory disease, distant metastasis, and dedifferentiation of thyroid cancer [[33], [34], [35]]. Understanding the correlation between TERT promoter mutation status and various clinicopathological factors can help predict the progression and prognosis of thyroid cancer.

This study aims to characterize the clinicopathological features of tumors in patients aged 70 and older with thyroid cancer, according to the latest World Health Organization (WHO) classification. By elucidating these characteristics, we seek to provide an evidence-based rationale to inform clinical decision-making.