A Histological Study of Polypoidal Stomach in Nemipterus japonicus off Visakhapatnam Coast

Background/Objectives: Histopathological screening of a typical polypoidal stomach and associated organs was performed on Nemipterus japonicus off Visakhapatnam coast. Methods: 1832 specimens were collected from Visakhapatnam coast at a depth of 45m-100m within the period January 2011 to December 2013 were examined for documenting lesions in the stomach. Of the total samples about 18% of fish were identified with typical mucosal polyps which were autopsied and tissues of skin, gill, muscle, stomach, intestine, liver, spleen, kidney and gonads of both normal and diseased fish were fixed in 10% buffered formalin for 48 hours and dehydrated in graded alcohols, followed by impregnation in paraffin. The embedded blocks are cut 5 μ thick on a microtome and sections stained with haemotoxylin and eosin, for the examination of pathological changes in the tissues. Findings: These studies revealed macroscopic lesions with a polyp arising from the mucosa of the gastric body leading to herniation of other digestive glands such as liver and pyloric caecum into the lumen of the polypoidal stomach. Histologically, the growth was differentiated as adenomatous polyp with abnormal proliferation of gastric mucosal glands in the stomach with focal erosion and hemorrhage. This evidence suggested chronic gastritis, but the cause of these unusual gastric polyps is unclear. Though earlier microbiological studies revealed the presence of enteric bacteria, with a dominance of Klebsiella pneumoniae, virological investigations failed to confirm any oncoviral particles and even aflatoxin analysis gave negative results. Immunological and karyological studies of N. japonicus with mucosal buccal polyps showed mitodepression. Application/Improvements: This is first histopathological report of this kind in N. japonicus and may help as a model for future studies on gastric polyposis in both human and animals.