A tumor composed of various tissues; such as, bone, hair, and teeth which are not normally found together at the site of origin and that are probably derived from embryonic remnants.

They most often occur in the ovary, where they are benign, and in the testis, where they are malignant.

1. In medicine, a true neoplasm made up of a number of different types of tissue, none of which is native to the area in which it occurs; most often found in the ovary or testis.
2. A tumour, especially of the gonads, characteristically formed of numerous distinct tissues and believed usually to arise from germ cells or their precursors.