Origin of immature teratoma of the ovary

Six cases of immature teratoma of the ovary were karyotyped and analyzed for chromosomal heteromorphisms, enzyme polymorphisms, and HLA specificities to determine their mechanism of origin. Three cases were chromosomally abnormal, with karyotypes of 48,XX, +14, +21; 47,XX, +20; and 47,XXX, respectively. The tumors with 48,XX, +14, +21 and 47,XX, +20 karyotypes were heterozygous for chromosomal heteromorphisms which were identical to those of their host and therefore originated from a premeiotic cell or failure of meiosis I. Both had a poor prognosis. The 47,XXX tumor and the three cases with normal karyotypes were homozygous for chromosome heteromorphisms and either homozygous or heterozygous for enzyme and HLA markers and therefore originated from a failure of meiosis II or duplication of a mature haploid ovum. All four had an uneventful postoperative course. These observations show that immature teratomas are like cystic teratomas in having at least three separate mechanisms of origin. However, they are unlike cystic teratomas in having a high proportion with chromosome abnormalities and a high rate of malignant transformation.