Immunohistochemical Study of Choledochal Cyst Wall

Introduction. Choledochal cysts are rare congenital anomalies that appear as localized cystic or fusiform biliary tree dilatations. Choledochal cyst is a rare congenital anomaly with a reported incidence of 1 in 100,000-150,000 live births (7). Nearly 25% of choledochal cysts are diagnosed in the first year of life and 60% in the first decade, but 20% detected are after the age of 20 years (12). Aim of the Study. The pathogenesis of choledochal cysts remains still unknown. The aim of this study was to examine relative distribution of growth factors, neuropeptide-containing innervation and apoptosis in the choledochal cyst wall. Materials and methods. Histopathological study of choledochal cyst wall was conducted on four patients aging from six months till 14 years. Tissues were processed for haematoxylin - eosin staining, immunohistochemistry for PGP 9.5, NGFR, NF, VEGF, CGRP and TUNEL method. Results. In overview sections we observed granulation tissue, blood vessel sanguineness and inflammatory infiltrate. Fibromuscular coat was thickened showing thick collagen bundles and dispersed smooth myocytes. Serosa was present in one case, all the rest demonstrated adhesions with dilated blood vessels and perivascular infiltrate. PGP 9.5 - containing nerve fibers and nerve fiber bundles were mostly observed in moderate and large amounts. NGFR in large amount was seen in nerve fiber bundles and nerve fibers among smooth muscle cells in the wall of small blood vessels. NF positive structures - nerve fibers and nerve fiber bundles - were found in moderate amount, except one case were the expression was very low. CGRP was found in neuroendocrine cells, nerve fiber bundles, leukocytes, inflammatory cells and endoteliocytes. Expression varied from low to moderately high. VEGF expression in most patient material was negative. Apoptosis was observed in inflammatory cells and epiteliocytes, showing large amount of positive structures. Conclusions. The amount of PGP 9.5 and CGRP demonstrates relatively good cyst wall innervation. Marked expression of NGFR proves still existing neuronal growth stimulation despite relatively unchanged neuronal cytoskeleton. Negative expression of VEGF proves lack of ischemia. Apoptosis mainly affects inflammatory cells and epiteliocytes, while the choledochal cyst wall presumably is composed of functionaly viable tissue.