Clinicopathologic and Genomic Features of Invasive Stratified Mucin-producing Carcinoma of the Uterine Cervix Coexisting With High-grade Squamous Intraepithelial Lesion.

Invasive stratified mucin-producing carcinoma (ISMC) is a specific type of adenocarcinoma of the cervix, which is associated with human papillomavirus infection and often coexists with other types of carcinomas. However, given its rarity, understanding of this disease remains insufficient. We present a unique case of ISMC of the cervix coexisting with a high-grade squamous intraepithelial lesion (HSIL). In addition to histologic and immunohistochemical feature observation, genomic profiling of the 2 lesions was performed. Histologically, the ISMC and HSIL lesions were independent of each other. Aside from the typical morphology, various architectural features of ISMC were observed. Immunohistochemically, the ISMC and HSIL lesions were strongly and diffusely positive for p16 and exhibited high Ki-67 expression. The ISMC lesion was also positive for CK7, MUC5AC, and MUC6, while it was negative for PAX-8. The HSIL lesion was positive for CK5/6 and p40. The combined positive score of PD-L1 was 55. The other markers were all negative in both lesions, and the p53 was wild-type. Next-generation sequencing analysis revealed multiple gene mutations in the ISMC and HSIL lesions. A total of 88 gene mutations were identified in the ISMC lesion, while 20 gene mutations were identified in the HSIL lesion. Three mutations (ERBB2, histidine decarboxylase gene [HDC], and BSN) were detected in the ISMC and HSIL lesions. Both lesions had a low tumor mutation burden and microsatellite-stable status. No copy number-associated variants or structural variations were identified in either lesion. These results suggest that patients with ISMC may benefit from PD-L1 immunotherapy and targeted therapy.