The aim of this research was to explain the etiology of pathological changes that have occurred on the body of goldfish (Carassius auratus). All samples were obtained from a fish farm that utilizes cooling water from the power station Dolna Odra. Since 2008 a few such cases have been sporadically observed there. An excised part of the tissue was analyzed based on histological assays and also by means of a transmission electron microscope (TEM). Histological staining showed that the tumor originated from the mesenchymal tissue with many blood vessels in its structure. The conducted research showed neither pathological changes caused by oncogenic viruses nor viral particles in the tumor tissue. Nevertheless, the most probable reason for these kind of changes is a combination of environmental factors and In Poland specific breeding conditions (warmed waters).
The study discusses the role of extracellular matrix (ECM) in the pathology of cumulative or storage diseases and in proliferative nonneoplastic lesions. The latter include keloid, nodular fascitis, generalised fibromatosis and gingival elephantiasis (fibrous hyperplasia of the gums). ECM also occurs at the sites where various substances released by the injured cells cumulate. The lesions result from degeneration (degeneration reflecting disturbed protein turnover, calcareous degeneration, mucoid degeneration, carbohydrate thesauroses and degeneration reflecting disturbed turnover of purines), disturbed circulation (oedema, thrombosis) and necrosis.