Intracranial ectopic pancreatic tissue.

In 2007 a young Japanese female was reported to suffer from a congenital brain malformation with a non-functioning pancreatic endocrine tumor arising from intracranial ectopic pancreatic tissue. Ectopic pancreas is normally confined to other endodermally-derived organs and not previously reported to be found in the brain. Therefore, we sought to better understand the true pancreatic nature of the tissue and to further understand the mechanism by which ectopic pancreas could appear in the brain. A detailed immunohistochemical analysis for pancreatic hormones, transcription factors, ductal/exocrine markers and stem cell markers on sections from the resected tumor tissue was performed. All five endocrine cell types are observed but pancreatic polypeptide cells are quite rare and ghrelin and glucagon cells are more numerous than in normal human pancreas. Insulin immunoreactive cells stain for c-peptide. The β-cell specific transcription factor, Nkx6.1, is expressed only in the insulin immunoreactive cells while neither Ptf1a or PDX-1 immunoreactive cells can be observed. Duct-like structures stain strongly for pan-cytokeratin and E-cahderin. The exocrine like tissue stains strongly for pancreatic amylase, lipase and chymotrypsin. Ngn-3 cells were very rare and not in the pancreatic area. Examining for endodermal markers we observed Sox17 had a weak staining in some areas of the pancreatic tissue but was much less widely expressed than FoxA2. The tumor tissue did not stain for the stem cell markers, Oct-4 and Sox2. It is speculated that the ectopic pancreas domain may arise from misexpression of homeodomain transcription factors related to Pdx1 within a domain of Ptf1a expression.