Osteogenic sarcomas in two fish species giant sea catfish (Arius thalassinus), and Delagoa threadfin bream (Nemipterus bipunctatu) caught from Saudi Arabia, the Arabian Gulf

During routine veterinary inspection of fish from fishing boats, fish auction yards, and fish landing stations, as well as the large fish market for detection of fish diseases, abnormalities and/or overgrowth in body surfaces and evaluation of hygienic conditions and fish quality at El-Jubail Province, Saudi Arabia., external neoplastic overgrowths were observed in two fish species, giant sea catfish (Arius thalassinus) and Delagoa threadfin bream (Nemipterus bipunctatu). In both fishes, the neoplasms appeared as bony masses, and it was hard in its consistency. In the giant sea catfish (Arius thalassinus), the tumor appeared as three multifocal hard swellings at different locations (in the head region, at the dorsal fin, and near the caudal fin). The tumor mass in the head region of this fish was observed at the base of the right angle of the lower jaw, and it was hard, bony, nodular to round, and of 0.7 cm in diameter. The second one was observed at the dorsal fin and appeared as a small oval to rod hard mass of 0.5 cm in diameter, while the third mass appeared as a large and irregular wart-shaped bony swelling, about 3 cm in diameter, that extended laterally on the left aspect of the caudal peduncle near the caudal fin. In radiographic examination, the neoplasm appeared small, round to large, irregular, dense bony overgrowth with variable sizes. In histopathological examination, evidences of fibro-osteosarcoma associated with prominent multiple rounded eosinophilic apoptotic bodies in the neoplastic bony trabeculae were observed. On the other side, the Delagoa threadfin bream (Nemipterus bipunctatus) showed only one yellowish to reddish, pedunculated, irregular, and very hard swelling at the base of the median site of the dorsal fin, and it was firmly connected to the spine of the dorsal fin; it was about 1 cm high with a wide base of 0.5 cm. In histopathological examination, the bony neoplastic masses in this fish appeared with massive edematous fibrous connective tissue and newly formed blood capillaries; abnormal mitosis, hemorrhages, and hemosiderin pigment deposition in the central and peripheral parts of the neoplasm were observed. New bone formation was confirmed using histochemical staining. Our results indicated that these two species are vulnerable to fibro-osteosarcoma. Further environmental investigations as well as immunohistochemical and molecular studies are required to indicate the potential impact of the environmental pollution on the incidence of the neoplasms in this locality and to correlate the cellular evidence of the neoplasms to a specific fish species.