Prognostic value of quantitative p63 immunostaining in adenoid cystic carcinoma of salivary gland assessed by computerized image analysis

BACKGROUND: In a long-term retrospective immunohistochemical study of adenoid cystic carcinoma (ACC) of salivary gland, we investigated the relation of p63 immunodetection to prognosis. Although it is generally agreed that the solid pattern is the most aggressive pattern of growth, ACCs with predominantly cribriform or tubular patterns have an unpredictable clinical course, with a relatively favorable 5-year survival but a low 20-year survival. METHODS: Formalin-fixed paraffin sections from 35 cases of ACC showing a predominantly better differentiated histopathology, ie, cribriform or tubular patterns of growth, were immunostained for p63. Automated image analysis was used to quantify p63 positivity, using a modification of a previously developed algorithm. RESULTS: Patients alive for more than 10 years had a lower extent of p63 expression than those who died of disease. Kaplan-Meier analysis revealed that separation of patients with morbidity and mortality from those alive with no evidence of disease, could be achieved at a cutoff of 35% p63 positivity (P = .0031, log-rank test). Multivariate analysis using the Cox proportional hazard model revealed p63 and tumor stage to be independent predictors of survival (P = .012 and P = .0003, respectively). CONCLUSIONS: To our knowledge, the present study is the first to report prognostic significance of p63 in salivary gland ACC and the first report of a robust and well-studied immunohistochemical stain performable on routinely fixed and processed tissue with prognostic utility.