Case report of chondroma in a grass carp (Ctenopharyngodon idella).

The grass carp (Ctenopharyngodon idella) is a herbivorous, freshwater fish species of the family Cyprinidae, and the only species of the genus Ctenopharyngodon. Neoplasms in fishes are generally less aggressive than neoplasms in mammals and are most commonly discrete, focal and benign neoplasms. A 3-year-old grass carp with a big mass on the vertebrae was referred to the clinic. According to the owner's statements, the fish had no signs of lethargy, ataxia and abnormal behaviors. The size of the mass was 7 × 6 × 6 cm. It cut hardly with audible sounds. The consistency of the mass was as hard as a cartilage. Microscopic examination revealed numerous irregular crests of hyaline cartilage beneath the skin. According to histopathologic characteristics, chondroma on the vertebrae of grass carp was diagnosed.