Pan-p63 but not ΔNp63 (p40) expression in undifferentiated carcinoma of the pancreas.

Undifferentiated carcinoma of the pancreas (UC) is a carcinoma without a definitive direction of differentiation. Tumour protein p63 is a regulator of squamous phenotype, which may also be engaged in tumour development. N-terminal isoforms of p63 are TAp63 and ΔNp63. Pan-p63 antibodies are able to detect both isoforms, whereas p40 antibodies recognise the ΔNp63 isoform only. The aim of the study was to describe pan-p63/p40 immunohistochemical expression patterns in pancreatic neoplasms: UC, ductal adenocarcinomas, neuroendocrine tumours, neuroendocrine carcinomas, serous cystic neoplasms, and solid pseudopapillary neoplasms. DAK-p63 and BC28 antibodies were used for pan-p63 and p40 detection, respectively. Moderate-to-strong pan-p63 was found in anaplastic (pleomorphic giant cell) UC (n = 4), sarcomatoid UC (n = 2), UC with osteoclast-like giant cells (n = 3), and ductal carcinomas with partial squamous differentiation. Weak and focal pan-p63 expression was found in monomorphic UC (n = 3) and in the majority of neuroendocrine carcinomas (6/7 cases). Pan-p63 expression was infrequent in ductal carcinomas without squamous differentiation and in neuroendocrine tumours. Serous cystic and solid pseudopapillary neoplasms were pan-p63-negative. Ductal carcinomas with partial squamous differentiation were the only tumours with evident p40 expression. Pan-p63(+)/p40(-) immunohistochemical status may be supportive for UC diagnosis. The pan-p63 expression was not equivalent to squamous differentiation in pancreatic neoplasia.