P53 Immunohistochemistry Defines a Subset of Human Papillomavirus-Independent Penile Squamous Cell Carcinomas with Adverse Prognosis

Penile squamous cell carcinoma (PSCC) is classified into 2 prognostically distinct types: human papillomavirus (HPV)-associated and HPV-independent. However, the impact of p53 status on prognosis remains controversial. We correlated HPV and p53 status with the prognosis of a large series of patients with PSCC. p53 was analyzed according to a recently described immunohistochemical (IHC) pattern-based framework that includes 2 normal and 4 abnormal patterns and closely correlates with TP53 mutational status. A total of 122 patients with surgically treated PSCC in 3 hospitals were included. Based on HPV in situ hybridization and p16 and p53 IHC, the tumors were classified into 3 subtypes: HPV-associated, HPV-independent/p53 normal, and HPV-independent/p53 abnormal. All patients were followed up for at least 22 months (median: 56.9 months). Thirty-six tumors (29%) were HPV-associated, 35 (29%) were HPV-independent/p53 normal, and 51 (42%) were HPV-independent/p53 abnormal. Disease-related deaths were observed in 3/36 (8%), 0/35 (0%) and 14/51 (27%) of the patients, respectively (P < 0.001). A total of 7/14 deaths in the latter group were patients with tumors showing p53 abnormal patterns not recognized in the classic p53 IHC interpretation (basal, null, and cytoplasmic). According to our multivariate analysis, HPV-independent/p53 abnormal tumors and advanced stage were associated with impaired disease-specific survival (hazard ratio = 23.4, 95% CI = 2.7-3095.3; P = 0.001 and 16.3, 95% CI = 1.8-2151.5; P = 0.008, respectively). In conclusion, compared with patients with HPV-associated and HPV-independent/p53-normal PSCC, patients with HPV-independent/p53 abnormal PSCC have worse clinical outcomes. p53 IHC results define 2 prognostic categories in HPV-independent PSCC: HPV-independent/p53-normal tumors as low-risk tumors, whereas HPV-independent/p53-abnormal tumors as aggressive neoplasms.