ABSTRACT
Determination of the tissue of origin of either normal or abnormal tissues in the body is usually reforred as histogenesis. Electron microscopy and immunohistochemical techniques have been used in the current experiment for histogenesis of one of the most agonizing kidney diseases, namely the renal cell carcinoma.40 kidneys were subjected after radical nephrectomy to immunohistochemical detection of the presence of intermediate filament cytokeratin, which is normally expressed in epithelial tissue and intermediate filament vimentin, which is normally expressed in mesenchymal non-myogenic cells. The kidneys were also examined by electron microscopy for detection of ultrastructure features that help determination the tissue of origin. From each kidney, two specimens were taken, one from the diseased area and another from far beyond the safety margin to serve as control. Additional control specimens were taken from nephrectomized kidneys for traumatic causes. Immunohistochemical study of the control specimens revealed expression of vimentin in the glomerular capillaries and expression of cytokeratin along the tubular epithelium. In cases of renal cell carcinoma, cytokeratin was expressed alone in 45% of cases, vimentin was expressed alone in 10% of cases and coexpression of both cytokeratin and vimentin was observed in 40% of cases while 5% of cases showed no expression. Electron microscopic study of the control specimens revealed the basic ultrastructure of the normal kidneys while the ultrastructure study of the diseased specimens revealed the basic features of the tumor. Expression of desmosomes was observed in almost all tumor specimens. The expression of the vimentin in some cases either alone or with cytokeratin was interpreted as a change in the characters of some tumor cells which indicates the need for additional techniques in such cases to get the proper interpretation. The prevalence of the expression of cytokeratin and the persistence existence of desmosomes indicate the epithelial origin of the tumor. The result of the current study is very beneficial for determining the line of therapy and follow up the patients. Moreover, it confirms the power of combined use of both immunohistochemistry and electron microscopy in histogenesis of any tissue with undetermined origin