Select updates in the pathology of kidney, testis, and penile cancer for 2026: Including FLCN-mutated (kidney) tumors, paratesticular mesothelial tumors, and TP53/HPV status in penile squamous cell carcinoma

Abstract

Herein, we have provided select updates targeted towards practicing pathologists pertaining to the pathology of kidney, testis, and penile cancer. This includes discussion of diagnostic criteria, evolution of nomenclature, emerging immunohistochemistry markers, diagnostic pitfalls, and improved understanding of prognostic significance of biomarkers and/or staging parameters. For kidney tumors, specific topics of discussion include a summary of the recent literature pertaining to the biology and diagnostic criteria for conventional and non-conventional FLCN-mutated tumors, utility of GPNMB immunohistochemistry, and diagnostic pitfalls relevant to eosinophilic solid and cystic renal cell carcinoma. Testicular/paratesticular updates address diagnostic criteria for mesothelium-derived lesions of the tunica vaginalis, recommended immunohistochemical panels for testicular sex cord-stromal tumors, and recommended nomenclature, specifically the use of "embryonic-type neuroectodermal tumor" rather than primitive neuroectodermal tumor (PNET) in the context of somatic transformation of testicular germ cell tumors. For penile squamous cell carcinoma, the summary emphasizes prognostic biomarkers, notably TP53 alterations and high risk HPV status, and nuances pertaining to pathologic staging.

Keywords: Birt-Hogg-Dubé syndrome; Complex mesothelial tumor of the tunica vaginalis; Embryonic-type neuroectodermal tumor; Eosinophilic solid and cystic renal cell carcinoma; FLCN-Mutated tumor; GPNMB; HPV; Mesothelioma; Mesothelioma in situ; Pathologic staging; Penile squamous cell carcinoma; Sex cord-stromal tumors; TP53; Well differentiated papillary mesothelial tumor.