Role of molecular pathology in tissue diagnostic of diseases of the gastrointestinal tract

Histopathology and immunohistochemistry constitute the diagnostic gold stan dard for most diseases of the gastrointestinal tract. Molecular pathology, i.e. the detection of specific DNA or RNA sequences, may be helpful in thos e cases which remain equivocal. Among the infectious agents that are routin ely detected in tissue specimens are mycobacteria. Whipple bacteria, CMV, H SV and HPV. Clonality assays are well established in non-Hodgkin's lymphoma s. In carcinomas of the gastrointestinal tract the detection of mutations o f Ki-ras, p53 and E-cadherin genes may be diagnostically helpful. Germ line mutations of several genes are important for the diagnosis of hereditary c ancer syndromes such as familial adenomatous polyposis (FAP) or hereditary non-polyposis colorectal cancer (HNPCC). The appropriate molecular genetic method for each case is selected on the base of histopathology and clinical information. The results of the molecular analysis has to be interpreted i n the synopsis of morphological and clinical data. In routine diagnostics, molecular pathology should be performed by a specially trained molecular pa thologist.