Ovarian teratomas in mice are derived from oocytes that have completed the first meiotic division.

Abstract

Spontaneous ovarian teratomas are found in about 50% of strain LT/Sv mice by the time they are 90 days old (Stevens and Varnum 1974). These teratomas result from parthenogenetic cleavage of ovarian oocytes. Some parthenotes reach a developmental stage equivalent to 7 d embryo before they become disorganised and further develop into a teratoma. Since some cleaved ovarian oocytes are accompanied by polar bodies, but others seem to lack them, it was uncertain whether the teratomas derive from oocytes that complete the first meiotic division or from oocytes that cleave mitotically without previous meiotic division.