# Association of a Number of Tumor Foci with Ultrasound Patterns and Reoperation Rate in Well-Differentiated Thyroid Cancer (WDTC)—A Single-Center Analysis

## TL;DR

This study examines how the number of tumor foci in thyroid cancer relates to ultrasound features and reoperation rates, finding limited clinical value in using this parameter.

## Contribution

The study reveals that the number of tumor foci is associated with ultrasound patterns but does not influence reoperation rates, challenging its clinical utility.

## Key findings

- The number of tumor foci is statistically associated with suspicious ultrasound features but not in a linear manner.
- No significant correlation was found between the number of foci and reoperation rates.
- Ultrasound patterns with the highest mean number of features were observed in patients with ≥4 foci.

## Abstract

Thyroid cancer (TC) is one of the most common endocrine malignancies, and accurate preoperative assessment is crucial for its optimal management. Ultrasound is the primary tool for diagnostic imaging, with features such as hypoechogenicity, microcalcifications, high vascularity, and irregular shape or margins often raising suspicion of malignancy. Another factor of interest is the number of tumor foci, which may influence prognosis and the choice of surgical strategy. In this study, we retrospectively analyzed 665 well-differentiated TC (WDTC) patients operated on between 2008 and 2024. We investigated relationships between the number of tumor foci, ultrasound patterns, and the reoperation rate. Our results showed a statistical association between the number of foci and suspicious ultrasound features, but the relationship was not linear. Importantly, the number of foci did not correlate with reoperation rates. These findings suggest that the number of tumor foci may provide limited additional value for TC diagnostics.

Background: Suspicious ultrasound patterns are essential for the accurate preoperative assessment of thyroid cancer (TC). The number of tumor foci may serve as an additional parameter, particularly when considered in association with ultrasound patterns and the reoperation rate. Methods: We conducted a retrospective analysis of 665 well-differentiated TC (WDTC) patients treated between 2008 and 2024. The analysis included preoperative data, ultrasound patterns (hypoechogenicity, microcalcifications, high vascularity, and irregular tumor shape or margins), and histopathological findings regarding the number of tumor foci and reoperation rates, additionally stratified by TNM stage and sex. Results: A statistically significant association was observed between the number of tumor foci and the mean number of ultrasound patterns (p < 0.05). The highest mean number of patterns was found with ≥4 foci (SD: 2.50 ± 1.20). However, this relationship was not linear, as in each focus category (1, 2, 3, and ≥4), the greatest number of ultrasound patterns consistently predominated. No significant association was found between a higher number of foci and a complete set of ultrasound patterns (p = 0.273) or the reoperation rate (p = 0.469). Analyses stratified by TNM stage and sex also did not reveal any significant differences (p > 0.05). Conclusions: Although the number of tumor foci demonstrates an association with ultrasound patterns, the lack of a consistent linear correlation and the absence of an impact on reoperation rates suggest that this parameter may provide limited additional clinical value beyond the general concept of multifocality.