Naturally Occurring Orocutaneous Papillomas and Carcinomas of Brown Bullheads (Ictalurus nebulosus) in New York State

Abstract

Ninety-four brown bullheads ( Ictalurus nebulosus) with spontaneous orocutaneous neoplasms (papillomas and carcinomas) were studied grossly and by light microscopy. Of these 94 fish, 71 were selected from 505 fish examined macroscopically during field surveys and 23 were selected from those submitted for diagnostic study. Fish with neoplasms came from 17 locations throughout New York State: Buffalo River, Canaan Lake, Cazenovia Lake, Delta Lake, Fort Pond, Greenwood Lake, Hudson River, Lake George, Lake Tiorati, Lincoln Hall Pond, Lincoln Pond, Oneida Lake, Onondaga Lake, Rutland Pond, Salmon River, Silver Stream Reservoir, and Swan Lake. The prevalence varied from 0 to 100%. Multiple neoplasms were more common (84/94, 89%) than solitary ones (10/94, 11%). In order of decreasing frequency, neoplasms arose on the head, especially the ventral aspect, the lower dental plate, the upper dental plate, the trunk, the barbels, the fins, the tongue, and the tail. Of the 38/94 brown bullheads (40%) with tumors in both upper and lower lips and dental plates, 24/38 (63%) had the tumors in opposition. Macroscopically, soft, pink or yellowish papillary masses protruded above the normal epithelial surfaces. Histologically, cutaneous and oral neoplasms originated from the morphologically similar Malpighian epithelial cells of the surface epithelia and from the outer cells of the enamel organ. Based on histopathologic criteria, cutaneous and oral neoplasms were considered the same disease in different anatomic locations. No apparent difference in biologic behavior was noted between cutaneous and oral neoplasms. The lesions apparently progressed from benign papilloma to locally invasive carcinoma (28/94, 30%). Neoplastic emboli were seen in one case, and no metastases were detected. There was no statistically significant difference between the susceptibility of males (20/57, 35%) and females (6/26, 23%) to carcinomas. An apparent correlation was noted between a higher frequency of malignant tumors and longer body size (3/ 13 fish [23%] <30 cm, 17/54 fish [31%] 30–34 cm, and 7/18 fish [39%] >34 cm).