Clinicopathological Features of Non-HPV-associated Common Differentiated Penile Squamous Cell Carcinoma: A Study of 55 Patients.

Abstract

To investigate the clinicopathological characteristics of non-HPV-related common differentiated penile squamous cell carcinoma, and to observe and analyze the changes of TP53 gene and the expression and significance of TP53, P16, programmed death-ligand 1 (PD-L1), epidermal growth factor receptor (EGFR), androgen receptor (AR), human epidermal growth factor receptor-2 (HER2), and Ki67 proteins in tumor tissue. A total of 65 patients with penile squamous cell carcinoma diagnosed from May 2008 to May 2020 in Yantai Yuhuangding Hospital were retrospectively analyzed, and tumors were confirmed as non-HPV-associated common differentiated squamous cell carcinoma of the penis with negative HPV molecular tests in 55 patients. The relevant clinicopathological data of 55 patients were collected, and the TP53 gene mutation was detected by applying first-generation sequencing technology. And tumor tissue microarrays were prepared, and further immunohistochemical EnVision 2-step method was used to detect the expression levels of 7 of these proteins: TP53, P16, PD-L1, EGFR, AR, HER2, and Ki67. Pathologic grading non-HPV-associated common differentiated penile squamous cell carcinoma of 55 patients was G1 in 22 patients, G2 in 28 patients, and G3 in 5 patients. The tumor pathologic stage was pT1 in 22 patients, pT2 in 26 patients, pT3 in 6 patients, and pT4 in 1 case. Immunohistochemical markers showed positive expression of TP53 protein in about 84% (46/55 patients) and strong positive expression in about 20% of patients (11/55 patients), and the expression level of this protein was closely related to the pathologic grade and stage of the tumor. All patients showed negative expression of P16 protein. PD-L1 protein-positive expression patients accounted for about 35% (19/55 patients), among whom strong positive expression patients accounted for 20% (11/55 patients), and there was a correlation between PD-L1 protein expression level and the maximum tumor diameter. EGFR protein was positively expressed in 76% (42/55 patients) of patients and confirmed a significant correlation with the pathologic grade and stage of the tumor. The percentage of Ki67 protein-positive expression patients was 58% (32/55 patients) and significantly correlated with tumor pathology grade. In contrast, AR and HER2 proteins were negative in all 55 tumors. In 55 patients, except for 10 patients with failed DNA extraction, the mutation rate of TP53 gene in the remaining 45 patients was about 33% (15/45 patients), and the mutation sites were mainly concentrated in exon 5, followed by exon 8 and exon 5/8 combined mutation, and occasionally in exon 7/8 combined mutation. TP53 gene mutations were present in all positive TP53 protein expression intervals, and the highest rate of TP53 gene mutations was found in patients with ≥80% strong positive expression of TP53 protein, about 67% (6/9 patients). In addition, statistical analysis revealed a significant positive correlation between TP53 and Ki67 protein expression, and a low correlation between TP53 and EGFR protein, PD-L1 and Ki67, and EGFR and Ki67 protein. Non-HPV-associated common differentiated squamous cell carcinoma of the penis currently dominates the morbidity, with relatively good pathologic grading/staging and prognosis for most tumors, with a few being poor. TP53 mutations play an important role in the pathogenesis of this tumor, but TP53 mutations do not always coexist with TP53 protein overexpression. The combination of 3 proteins, TP53, P16, and Ki67, are useful antibodies for adjuvant staging and prognosis of penile squamous cell carcinoma. PD-L1 and EGFR are important new biological targets for adjuvant therapy in non-HPV-associated common differentiated squamous cell carcinoma of the penis, whereas AR and HER2 proteins were not clearly targeted in all patients. In conclusion, the combined detection of 5 proteins, TP53, P16, PD-L1, EGFR, and Ki67, in addition to AR and HER2, is important for the precise diagnosis and prognosis analysis of non-HPV-associated common differentiated squamous cell carcinoma of the penis.