Expression of p16^Ink4aprotein in pleomorphic adenoma and carcinoma ex pleomorphic adenoma proves diversity of tumour biology and predicts clinical course

Abstract

AimsThe aim of the study is to correlate p16Ink4a expression with the clinical courses of pleomorphic adenoma (PA), its malignant transformation (CaexPA) and treatment outcomes.MethodsRetrospective analysis (1998–2019) of 47 CaexPA, 148 PA and 22 normal salivary gland samples was performed. PAs were divided into two subsets: clinically ‘slow’ tumours characterised by stable size or slow growth; and ‘fast’ tumours with rapid growth rate.ResultsPositive p16Ink4a expression was found in 68 PA and 23 CaexPA, and borderline expression in 80 and 20, respectively. All 22 (100%) normal salivary gland samples presented with no p16Ink4a expression. Significant difference in p16Ink4a expression was observed between normal tissue, PA and CaexPA (χ2 (4)=172,19; p=0.0001). The PA clinical subgroups were also evaluated separately, revealing additional statistical relations: ‘fast’ PA and CaexPA differed significantly in p16Ink4a expression (χ2 (2)=8.06; p=0.01781) while ‘slow’ PA and CaexPA did not (χ2 (2)=3.09; p=0.2129). 3-year, 5-year and 10-year survival among p16Ink4a positive CaexPA patients was 100%, 90.56% and 60.37%, respectively, and in CaexPA patients with borderline p16Ink4a expression was 90.0%, 73.64% and 22.20%, respectively. Statistically significant difference between expression pattern and survival rate was observed (F Cox test – F (16, 24)=2.31; p=0.03075).ConclusionsOur study confirms no p16Ink4a expression in normal tissue, but reveals differences in expression between ‘fast’ and ‘slow’ PA. We suggest that p16Ink4a overexpression is connected to PA proliferation and subsequent malignant transformation to CaexPA. Borderline p16Ink4a staining correlates with worse prognosis of CaexPA.

Global DNA Methylation Profiling Reveals Differentially Methylated CpGs between Salivary Gland Pleomorphic Adenomas with Distinct Clinical Course

“…Such an approach is novel in the context of PA as the previous reports have rather examined selected genes as potentially methylated in PA and/or the subsequent CaexPA and were not related to the differential course of PA [ 22 , 23 , 24 ]. In contrast, in our recent paper, we revealed differences in p16Ink4a protein expression between FGT and SGT PAs and demonstrated that its overexpression is connected to PA proliferation and subsequent malignant transformation to CaexPA [ 21 ].…”

“…Recent decades have brought a marked increase in the incidence of salivary gland tumors [ 5 , 12 , 20 ]. Among them, pleomorphic adenomas are the most frequent, and as previously observed, their development may vary in the context of tumor growth rate and malignant transformation [ 12 , 21 ]. On one hand, at the stage of initial diagnosis, both pathologists as well as clinicians are not able to assign the tumor to the fast-growing or slow-growing cohort.…”

Expression Features of Human Papilloma Virus Type 16 and Anti-Epstein-Barr Virus in Pleomorphic Adenoma, Surrounding and Intact Salivary Gland

“…Bartkowiak E. et al showed that human papilloma virus type 16 overexpression was connected with pleomorphic adenoma proliferation and subsequent malignant transformation to carcinoma (carcinoma ex pleomorphic adenoma) [12].…”

Molecular Factors in Carcinoma Ex Pleomorphic Adenoma: Systematic Review and Meta‐Analysis

“…Comparison against PA and SDCDN were both nonstatistically significant (Supplement 2.9). 50,51,62 p16 Five studies (n = 171) reported p16 incidence, 48,[75][76][77][78] with four (n = 134) available for meta-analysis. The reading from the nucleus of malignant p16 cells were used when multiple p16 readings were reported.…”

“…76 Three studies reported on IHC overexpression of p16Ink4a protein, with high and statistically significant heterogeneity between studies. [75][76][77] Tourne et al used an IHC-based quantification score to identify if median p16 expression was lower in PA than CXPA. 48 Two studies reported methylation incidence.…”