Benign ovarian teratoma in a red-eared slider turtle (Trachemys scripta elegans)

TERATOMAS are neoplasms that arise from pluripotent germ cells that differentiate into tissues from two or three of the embryonic layers (ectoderm, mesoderm and endoderm) (Gurfield and Benirschke 2003) and may undergo germi-native or embryonic differentiation. They are composed of multiple tissues that are foreign to the part of the body in which they arise (Miyoshi and others 2001). Theories about the origin of teratomas suggest a parthenogenetic origin from a single germ cell during the transition between the first and second meiotic division, before the extrusion of the first polar body (Linder and others 1975, Oliveira and others 2003) Based on the degree of anaplasia or the presence of undiffer-entiated elements resembling those of the embryo, teratomas may be classified as benign (mature) or malignant (imma-ture). They arise mainly from the gonadal tissues, although extragonadal cases sometimes occur; intracranial, peritoneal and retroperitoneal teratomas have been reported (Newman and others 2003).Cases of teratoma have frequently been reported in mam-mals (Clayton 1975, Frisk and others 1978, Frye 1983, Gupta and Sarmah 1985, Wilson and others 1985, Jergens and oth-ers 1987, Basaraba and others 1998, De Bosschere and others 1999, Miyoshi and others 2001, Gurfield and Benirschke 2003, Catone and others 2004), birds (Hamir 1985) and amphib-ians (Cheong and others 2000). Teratomas have also been reported in reptiles, although they are not frequently diag-nosed (Machotka 1984, Anderson and others 1996, Hertha and others 2000, Tocidlowski and others 2001, Newman and others 2003). Another type of gonadal neoplasm, dysgermi-noma, has been described in the snapping turtle (