In this habilitation treatise the current situation in diagnosis of canine carcinomas is showed. It begins with state of the art reviews of the cytoskelett, the immunohistochemistry and the protein analysis. An epidemiological analysis of 11387 autopsy cases (1980 - 1997) follows showing that cancer is one of the most threatening disease in dogs. The study is continued by an immunolocalization study of papillomavirus antigen in canine tumors, and studies of the cytokeratin composition of different neoplasias (heart, skin, mammary tissue, liver) and lymph node metastasis. All in all it could be shown that a cytokeratin typing is very useful to differentiate epithelial neoplasias, and can give a help to find the origin tissue of a metastasis.
