Benign tumors in swim bladder and deformity of notochord juvenile cod rearing in cage and basin from different farms in the North of West Europe | Новообразования в плавательном пузыре и деформации скелета молоди трески, выращиваемой в садках и бассейнах различных ферм на севере Западной Европы

Normally swim bladder is located retroperitoneal in dorsal part of abdominal cavity. It is surrounded by thin fibrous tunica externa, and gas gland at proximal / cranial pole of a swim bladder. The gas gland is composed of accumulation of epithelial cells with eosinophilic cytoplasm and round-oval vesicular nuclei with small nucleoli. Gas gland is vascularised by rete mirabilis. The analysis of cod larvae revealed the proliferative lesions. Hyperplasia. Varying degree of hyperplasia was observed in 37 specimens. Simple and partially papillary hyperplasia was observed composing of thee increased number of epithelial cells with eosinophilic cytoplasm, somewhat enlarged vesiculous nuclei with prominent nucleoli. In some areas there were papillae formations with central fibro vascular core covered by epithelial cells. There was no necrosis of the cells. Granuloma formations. In one case at the distal end of the swim bladder a granulomatous lesion was found outside the tunica externa in the oedematous connective tissue. The granuloma was composed of epitheloid cells with vesiculous nuclei with small nucleoli and central necrosis. Adenoma. Adenoma was observed in 19 cases. They were well defined, the masses varying in size from 1 to 2 milli m. They were basically well defined accumulations of epithelial cells with mild degree of pleomorphism and enlarged vesiculous nuclei with prominent nucleoli. No mitotic figures were observed. In one case there was central necrosis with calcification. In the absence of significant pleomorphism, hyperchromasia, normal or abnormal mitosis, these lesions were considered to be adenoma. Some lesions were so large that they filled up the whole cavity of a swim bladder. In some cases the lesions caused significant enlargement of a swim bladder due to formation of large tumor, which pressured on notochord and resulted in vertebral deformation of kyphosis type