Multinucleated cells, often simply called giant cells, are found in a variety of situations in teleost fish. They are not uncommon in granulomatous inflammatory responses, such as bacterial kidney disease, proliferative kidney disease, or as a response to vaccine, and are a result of fusion of macrophages or epithelioid cells. They are also found in virus infections, so-called syncytial giant cells, in which a number of non-macrophage cells, such as hepatocytes, fuse together. But giant cells are also found in normal fish as osteoclasts. Although...
![Figure 1. Multiple giant cells in the peritoneal cavity of salmon, a response to vaccine, its bright red character apparent (arrows). Similar to so-called Splendore-Hoeppli reactions (asteroid bodies).](https://sp-ao.shortpixel.ai/client/to_webp,q_glossy,ret_img,w_700,h_464/https://fishhistopathology.com/wp-content/uploads/2019/05/feature-image-1.jpg)