TP53 Mutations and PD-L1 Amplification in Vulvar Adenocarcinoma of the Intestinal Type: Insights From Whole Exome Sequencing of 2 Cases.

Abstract

Vulvar adenocarcinoma of the intestinal type (VAIt) is a rare subtype of primary vulvar carcinoma, with ∼30 cases documented in the English literature. This study presents 2 new cases of HPV-independent VAIt with lymph node metastasis and discusses their clinical presentation, histopathologic features, and whole exome sequencing (WES) analysis. Both cases exhibited histologic features consistent with VAIt, including tubular, papillary, and mucinous carcinoma components. Immunohistochemical analysis showed p16 patchy staining, CDX2, CK20, and SATB2 positivity, while being negative for ER, PAX8, and CK7. WES revealed pathogenic TP53 mutations in both cases, accompanied by distinct additional mutations (GRIN2A and KDM6A in Case #1; CHD4 in Case #2). Common copy number alterations (CNAs) included TP53 loss of heterozygosity and CD274/PD-L1 amplification. However, other CNAs varied between the cases. Immunohistochemistry for p53 suggests the presence of both wild-type and mutant subclones, indicating that TP53 abnormalities may be acquired during tumor progression. Both tumors showed mutational signatures SBS1 and SBS5, associated with aging and DNA damage. Our findings deepen the understanding of the genetic events involved in the tumorigenesis of HPV-independent VAIt. Given the TP53 abnormalities and CD274/PD-L1 amplification, emerging p53-based therapies and immune checkpoint inhibitors may represent potential treatment targets. While these findings contribute to the understanding of VAIt tumorigenesis, further research is required to validate these observations in a larger cohort.