After a routine checkup of a four-month-old baby boy last year, doctors discovered that his head was growing at an excessively rapid rate. The doctors ordered an MRI scan, which revealed that the boy had a rare tumor that had something even more rare growing inside of it -- several fully grown teeth. Although the discovery occurred last year in Maryland, the details were recently made public for the first time when they were published in a medical journal.

While there are different types of tumors that can contain hair, bone and teeth, this is believed to be the first of this particular type of brain tumor to have fully formed teeth. The tumor itself was big -- it measured about about 4 centimeters in diameter.

But this story has a happy ending. Although the boy will have to receive hormone treatments and regular MRI scans to make sure the tumor doesn't return, the tumor-teeth were removed, they are now being studied by scientists, and the boy should live a relatively healthy, normal life.

By the time the teeth were removed, they were thought to be the size of the adult human teeth that grow in adults' lower jaw.

This is not the first or last case where doctors were stunned to discover what the human body can grow inside of itself. In the past, doctors have found human hair and even plants growing inside of people.