Histopathological and Immunohistochemical Diagnostic of Carcinosarcoma of Mandible in a Rainbowtrout (Onchorhyincus mykiss)

ABSTRACT

Background: The most common health problems described in fishes are noninfectious, infectious, and metabolic disorders. Fishes have neoplasias that are similar to those observed in mammals. Though these neoplasias do not cause economic losses to aquaculture, they have aroused a crescent interest from the comparative pathology’s point of view. Neoplasias of the oral cavity in fishes are usually reported as individual cases, but mandible tumors are not common, and most of them are squamous cells carcinomas. The aim of this study is to report a case of carcinosarcoma of the mandible in a rainbow trout (Oncorhynchus mykiss), obtained from a trout farm in Campos do Jordão, São Paulo, Brazil. Case The fish underwent necropsy and tissue samples were collected and fixed with a buffer-neutralized formalin solution, which were then embedded in paraffin, sectioned in 5 μm sections and stained with hematoxylin-eosin. The histological sections were stained for immunohistochemical procedures, according to a modified avidin-biotin-peroxidase complex technique. Slides containing tissue were deparaffinized with xylol and rehydrated with alcohol of different grades. The endogenous peroxidase activity was blocked by incubating the slides for 20 min at 0.3% H2O2 in a solution of 5% methanol. After rinsing the slides in water and in a PBS/0.05%-Tween 20 solution, they were incubated in normal serum diluted 1100 containing 10% bovine albumin in PBS (BSA), at room temperature for 30 min in humid chamber. After incubation, the primary anti-cytokeratin and anti-vimentin antibody was added to a 1200 dilution in 10% PBS-BSA, and the slides were incubated until the next day at 41oC in humid chamber. The slides were then rinsed in PBS and incubated for 7 min in a 50 mL 30.3-diaminobenzidine solution containing 1% PBS-BSA in 50 mL H2O2. Hematoxylin was used for counterstaining. The immunohistochemical analysis showed a tumor with epithelial and mesenchymatous neoplastic components.(...)