Fine structure of the organic matrix of human pancreatic stones.

Pancreatic stones that were removed from the pancreatic ducts of patients with chronic calcifying pancreatitis were decalcified so the organic matrix could be studied by scanning and transmission electron microscopy. The observations made by scanning electron microscopy were compared with those made on undecalcified stones, and the findings were correlated with light microscopic observations. After the calcium carbonate was removed, the stones consisted of multiple partitions arranged like a sponge. They were embedded in a gel-like matrix. The organic partitions frequently were composed of dense surface layers and sparse central reticular accumulations, which had surrounded and bound calcium carbonate crystals. The organic matrix was heterogeneous in texture. Some areas had dense, regular, proteinaceous fibrous material. Deposits resembling fibrin were observed. Altered cellular constituents appeared to make up minor portions of the matrix. Calcium carbonate, which was precipitated in vitro in pancreatic juice, resembled the morphology of pancreatic stones more than that of pure calcium carbonate crystals. These results are consistent with the coformation of pancreatic stones from constituents in the pancreatic juice [including pancreatic stone protein (PSP), glycosaminoglycans, and occasional cells] and precipitated calcium carbonate.