Whole-Exome Sequencing Reveals Hippo Pathway Mutations as a Hallmark of Aggressive PTMC in Young Males

Background Papillary thyroid microcarcinoma (PTMC) is typically associated with an excellent prognosis, and active surveillance is often appropriate for tumors smaller than 0.5 cm. However, surgical intervention is warranted when there is evidence of tumor progression or suspicion of lymph node metastasis. This study aims to characterize the genetic alterations associated with lymph node metastasis in PTMC to inform risk-adapted surgical management. Methods DNA was extracted from primary tumor tissues of 42 PTMC patients with central lymph node metastasis and 30 patients without metastasis. Whole-exome sequencing (WES) was performed for both groups, and somatic variants were analyzed using the maftools package in R. Mutational signatures were compared against reference profiles from the COSMIC database. Statistical analyses were conducted to evaluate the prognostic significance of the identified variants. Results Patients with lymph node metastasis were significantly younger and more frequently male compared to those without metastasis. Whole-exome sequencing revealed a higher somatic mutational burden in the metastatic group, along with distinct mutational signatures, including an enrichment of COSMIC Signature SBS89. Recurrently mutated genes such as BRAF , FGFR1 , and CREBBP were identified across the cohort, while comparative analysis between primary tumors and lymph node metastases demonstrated divergent mutation profiles. Notably, male patients with lymph node metastasis exhibited frequent missense mutations in FAM98A , CYP26B1 , and EPS8L3 , as well as exclusive alterations in key components of the hippo signaling pathway, including YAP1 , TEAD1 , and WNT16 . Pathway-level analysis confirmed significant enrichment of hippo pathway mutations in this subgroup, suggesting a potential sex-specific molecular mechanism underlying metastatic progression in PTMC. Conclusions This study highlights that PTMC with lymph node metastasis, particularly in male patients, exhibits distinct genomic characteristics, including enrichment of COSMIC Signature SBS89 and recurrent mutations in components of the hippo signaling pathway. These findings underscore the potential value of molecular profiling in identifying high-risk subgroups and optimizing individualized management strategies in PTMC.