Immunohistochemical study of pancreatoblastoma

Alpha fetoprotein-producing acinar cell carcinoma of the pancreas showing multiple lines of differentiation

An alpha fetoprotein (AFP)-producing tumour occurring in the head of the pancreas of a 30-year-old woman is reported. Histological examination revealed a markedly solid proliferation of tumour cells with prominent nucleoli and occasional luminal structures, some of which contained mucinous material stained with mucicarmine and alcian blue. No squamoid corpuscles were recognized. Immunohistochemistry showed intense positivity for lipase trypsin, and AFP basically, and single cells were also positive for carcino-embryonic antigen, CA19-9, synaptophysin and neuron-specific enolase. Pancreatic hormone-positive cells were absent. Electron microscopical examination revealed numerous granules of variable sizes in the tumour cells, which were considered to be zymogen. The tumour is an acinar cell carcinoma with multi-directional differentiation including the ability to produce AFP. Among AFP-positive pancreatic tumours, acinar cell carcinoma and pancreatoblastoma seem to be the most frequent.

Pancreatoblastoma in an adult: its separation from acinar cell carcinoma

Pancreatoblastomas are rare tumours, which usually occur in childhood. Here we describe a pancreatoblastoma in a 39-year-old woman. The tumour was located in the tail of the pancreas and consisted of cells forming well-differentiated acinar structures and scattered solid components ("squamoid corpuscles"). Immunocytochemically, the acinar components were positive for pancreatic enzymes and pancreatic stone protein, while the cells of the "squamoid corpuscles" lacked these markers. There was no p53 overexpression nor any mutation at codon 12 of the Ki-ras oncogene. The main differential diagnosis of this tumour was acinar cell carcinoma, because both tumours have a number of features in common (scattered solid components, positivity for pancreatic enzymes, lack of p53 overexpression and of Ki-ras mutation). Findings which distinguished the pancreatoblastoma and separated it from acinar cell carcinoma were the negativity of the solid components ("squamoid corpuscles") for neuroendocrine markers and their very weak keratin positivity. As the patient is alive and well 30 months after tumour resection, this pancreatoblastoma also differs in biology from the usual acinar cell carcinoma.