Analyses of CTNNB1 mutation and expression and clinicopathological characteristics in 179 cases of solid-pseudopapillary neoplasm of the pancreas.

Background: Nuclear expression of CTNNB1 is occasionally negative in solid-pseudopapillary neoplasm (SPN) of the pancreas, leading to a missed diagnosis. In the present study, we aimed to investigate the clinical significance of CTNNB1 mutation detection for diagnosing SPN and explore the difference in clinicopathological characteristics at different ages and sex.

Methods: Patients who underwent surgery for a pathologically confirmed SPN in our institution between 2011 and 2020 were collected. Their clinicopathological data were analyzed.

Results: The median age of the 179 patients was 31 years (6-64 years), including 34 pediatric patients (19.0%), and 32 patients were male (17.9%). We detected point mutations in exon 3 of CTNNB1 in 74.3% (133/179) of SPNs by Sanger sequencing. The main mutation sites were D32, S33, S37, G34 and T41. In the three SPNs without nuclear expression of CTNNB1, Sanger sequencing showed point mutations of CTNNB1. NGS did not detect any consistent mutation except CTNNB1 in the three cases. The tumor size, Ki-67 index, and the negative rates of CTNNB1 nuclear expression and synaptophysin expression in the pediatric group were higher than those in other groups (p < .05).

Conclusions: For atypical cases, testing for CTNNB1 mutations can help in the accurate diagnosis of SPN. Compared with adult patients, pediatrics with SPN may be more prone to recurrence, and their immunohistochemical phenotype is more complex, requiring additional care in the diagnosis and postoperative follow-up.