TUMORIGENESIS AND TUMOR MARKERS IN FISH: AN UPDATED REVIEW

Fish is the largest class of vertebrates. Neoplasia is a known disease in fishes which is not considered to be a deadly condition for few malignancies. Cancer is the unregulated cell proliferation with the ability to invade or metastasize to other parts of the body. The tumorigenic process is marked by a competition between cellular proliferation and apoptosis characterized by genetic mutations and increased connective tissue proliferation with associated impairment of the immune system. Tumor markers are molecules produced by tumor cells or other cells of the body in response to cancer or benign conditions and thus; are of diagnostic value. Most tumor markers are secreted into blood and are assayed in blood, urine or immuno-histochemically. Diagnosis of tumors in fish is not always easy to carry out, and the tool provided by antibodies used on mammalian tissue is essential for obtaining definitive, unambiguous, and inexpensive identification. Generally, teleosts resemble other vertebrates in their predisposition to neoplastic lesions, which been widely studied, characterized, and classified. Immunohistochemistry is an extremely useful technique for the diagnosis of neoplasms. This technology relies upon antibody-based stains specific for intermediate filaments or surface markers. This review discusses the currently available tumor markers for different neoplasms in fish as well as the mostly used tumor markers in diagnosis. The objective of this review also is to provide an overview of neoplasia and the various neoplastic disease conditions in fishes as well as the most common methods used in diagnosis of fish tumors including immunohistochemistry and tumor markers.