Abstract
The morphological characteristics of tumors which developed around the mouth of chum (Oncorhynchus keta) and masu salmon (O. masou) after surviving an experimental infection of Oncorhynchus mason virus (OMV) were studied histopathologically.
The tumor tissues from the jaw of chum and masu salmon were composed of epithelial cells with the large light nuclei. The tumor was considered to be malignant epithelioma because of its active proliferation and intensive invasion of the connective tissues.
Tumors which developed on the corneal epithelium and inneropercular of chum salmon showed similar characteristics to those around the mouth. Two types of tumor tissues also appeared in the kidney. One of them showed similar characteristics to those around the mouth and was presumed to be a transferable tumor. The others were characterized by their hyperplastic renal tuble cells (tuble epithelial cells) and their similarity in appearance to smooth muscle fibers.
