## 4 Discussion  
According to these preliminary results, preoperative evaluation of the TT and DOI parameters by means of UHFUS appeared to significantly correlate with histology. A minimal and clinically acceptable overestimation was found for UHFUS DOI measurements, while TT was underestimated by 0.1 mm. We might speculate that higher frequencies allowed better visualization of tumor margins, providing reliable measurements of the lesions' dimensions; however, it should be noted that histological TT measurements appeared to be higher than the UHFUS measurements in the absence of statistically significant differences. Although the UHFUS scan was performed avoiding the compression of the lesion, it cannot be excluded that minimal pressure was applied, resulting in reduced TT UHFUS dimensions compared to histology. Intraoral US is a well-established technique that has been previously described in the literature, and US-based parameters are prognosticators in terms of oncological outcomes during and after the management of oral cancer [4]. TT was the most frequently employed US parameter for the assessment of the longitudinal extension in terms of the depths of oral cavity tumors prior to the introduction of DOI as a T-category modifier [9; 25]. Although both TT and DOI appear strongly correlated with the risk of presence of nodal metastases, albeit with different predictive cut-off limits, at present DOI is the parameter of choice due to its higher reliability [7]. Nevertheless, combined TT and DOI evaluations can be useful in terms of staging and prognosis, especially in small tumors where the issue of occult metastases is extremely relevant. [PERSON] et al. reported that US TT measurements showed strong correlations with histology, especially in the assessment of tumors >10.0 mm [11]. [PERSON] et al. [26] employed US both preoperatively and intraoperatively. While preoperative TT assessments appeared to be reliable compared to histology, the intraoperative assessment of deep resection margins had moderate predictive value due to tissue compression. Moreover, US measurements have been reported to have a predictive value for the development of nodal metastases, potentially influencing the therapeutic approach [27; 28]. [PERSON] et al. [29] evaluated TT and tumor margins to grade the malignancy of tongue tumors and set a thickness of 8 mm as the cut-off point to predict the risk of developing neck metastases. [PERSON] et al. [30] reported that DOI was a relevant variable, especially in clinical T1 N0 disease, which could give indication of the performance of neck dissection. Finally, [PERSON] et al. [31] found a significant correlation between DOI and histology, suggesting a potential role in the assessment of the aggressiveness of the tumor, as well as supporting the choice of the optimal treatment. Overall, US was reported to be superior to CT and MR, especially in cases of thin tumors with TT < 5 mm [5]; however, over- or under-estimation can occur due to the presence of inflammation or to the pressure applied by the US probe [4]. Other factors accountable for the discrepancy between US and histology measurements can be the shrinkage of the resection specimen during formalin fixation and slicing errors from the cutting plane during histological processing, which have been reported to range between 10 and 20% [32]. Nevertheless, the decrease in tumor size between post-excision andpost-formalin fixation was reported to be around 4.7% in the absence of significance [32]. In our sample, a minimal discrepancy was observed between UHFUS and histological measurements, which did not reach statistical significance. It could be hypothesized that the increased conspicuity obtained by means of the higher frequencies employed may have improved the preoperative assessment of OSCC lesions. Interestingly, UHFUS measurements were relatively smaller than histology measurements when evaluating the TT parameter. This fact could be related to the application of a slight pressure on the tumor, which can occur during the UHFUS scan.