Abstract: Fishes found in polluted waters is susceptible to get affected by tumors which forms the base of the present study. The study is focused on Mytus gulio, a resident along the Veli lake stretch. This lake gets polluted from the nearby industrial stretches and also by human activities. On behalf of the study it was observe that the fishes were affected by tumour which was reddish in color with an unpigmented multilobular growth found at the caudal peduncle of the fish. Fusiform cells arranged in parallel arrays, multinucleate giant cells, pleomorphic cells and focal areas of hemorrhage with nests of tumor cells were interspersed throughout the tissue. Disposition of the vertebra, dysplastic vertebral bone, conical protrusion under the skin and at the base of the caudal fin etc. were noticed which is said to be the histopathological symptoms of erythrophorma, the tumor. The occurrence of these deformities was attributed to the intensity of industrial as well as sewage pollution in the environment. Through, the study it was found that infectious causes of deformities were of high percentage, so more studies and researches are to be done in the field and effective preventive measures must be put forward.