How a Tumor Can Grow Hair and Teeth
Some tumors called teratomas can contain hair, teeth, bone, or other tissue that seems startlingly out of place. These growths most often develop from germ cells—the reproductive cells that can give rise to eggs or sperm. Unlike most body cells, germ cells have the potential to develop into many different kinds of tissue.
If a germ cell begins dividing abnormally, its descendants may mature into a jumble of tissue types inside one mass. A teratoma can therefore contain structures such as skin, which may produce hair, alongside cartilage or tooth-like material. These are tissues organized within the tumor, not evidence that a complete person or functioning organ is forming.
Why the Contents Vary
The tumor’s appearance depends on which kinds of tissue its cells develop into. Some teratomas are made mostly of mature, recognizable tissues; others contain less-developed cells. The name covers a range of growths, so finding hair or teeth is possible, not inevitable.
The key is that the tumor is not deliberately building a body part. It is the result of cells with unusually broad developmental potential dividing in the wrong place and differentiating—the process by which cells take on specialized forms—without the normal organization that guides development. That combination can produce a mass containing tissue from several parts of the body, even though it has no coordinated plan.
