Isochromosome 1q as the sole chromosomal abnormality in two fetal teratomas. Possible trisomic or tetrasomic zygote rescue in fetal teratoma with an additional isochromosome 1q.

An isochromosome of the long arm of chromosome 1 leading to tetrasomy 1q was detected as the sole chromosomal aberration in two cases of fetal teratoma arising from the oral cavity. This type of teratoma is extremely rare and has seldom been investigated cytogenetically. Studies of DNA markers in the tumor, normal fetal skin, and parental cells demonstrated that in both cases the additional 1q material was of maternal origin. In one of the patients, the teratoma had maternal 1q marker alleles that were not found in the fetal body cells. This implies that the tumor was not derived in a direct way from the fetal body tissue; instead, the chromosomally-normal fetus might be the result of some trisomic or tetrasomic zygote rescue mechanism.