Abstract
Histopathological study based on the anatomy of the lymphatic system was carried out to clarify the metastatic routes in a case of feline peritoneal mesothelioma. Two routes, via sternal lymphatic drainage and the intestinal lymph trunk, were involved in the metastasis from the peritoneal to the thoracic cavity. The case seems to be a good example of a spontaneous tumor which proves the importance of lymphatics in the initial stage of tumor metastasis.