A specific type of rare brain tumor has caused a 4-month-old infant in Maryland to be the first person to have had teeth form in his brain, according to a news report of the case.

Once the tumor was removed from the boy's brain, doctors said this specific case helped them understand how rare tumors develop over time, LiveScience reported.

Now that the tumor has been removed, the boy is doing well.

The boy's rare occurrence was first noticed by the doctors when the child's head appeared to be growing faster than is typical for children his age. Upon scanning his brain, it was revealed that a tumor containing structures that looked very similar to teeth, normally found in the lower jaw, had developed inside.

When the brain surgery was being conducted for the tumor to be removed from the child's brain, the doctors found that the tumor contained several fully formed teeth, according to the report.

After an analysis of tumor tissue, doctors determined the child had a craniopharyngioma, a rare brain tumor that can grow to be larger than a golf ball, but does not spread, according to LiveScience.

Although these tumors were always suspected by researchers to have formed from the same cells involved in making teeth, until now, they had never come across actual teeth in these tumors, said Narlin Beaty, a neurosurgeon at the University of Maryland Medical Center, who performed the boy's surgery along with his colleague, Dr. Edward Ahn, of Johns Hopkins Children's Center. 

"It's not every day you see teeth in any type of tumor in the brain. In a craniopharyngiomas, it's unheard of," Beaty said.

Craniopharyngiomas commonly contain calcium deposits, "but when we pulled out a full tooth...I think that's something slightly different," Beaty told Live Science.

Tumors known as teratomas, which are unique among tumors because they contain all three of the tissue types found in an early-stage human embryo, have had teeth form in people's brains, Beaty said.

However, craniopharyngiomas have only one layer of tissue, LiveScience reported.

Since this boy's case, it more certain that craniopharyngiomas do indeed develop from the cells that make teeth, Beaty said.

These tumors are most often diagnosed in children ages 5 to 14, and are rare in children younger than 2, according to the National Cancer Institute.

"The boy is progressing well in his development, the researchers said. However, because craniopharyngiomas are tumors of the pituitary gland - a gland in the brain that releases many important hormones - they often cause hormone problems," LiveScience reported.

In the boy's case, the tumor destroyed the normal connections in the brain that would allow certain hormones to be released, Beaty said, so he will need to receive hormone treatments for the rest of his life to replace these hormones, Beaty said.

"He's doing extremely well, all things considered," Beaty said. "This was a big tumor right in the center of his brain. Before the moderate surgical era, this child would not have survived," Beaty said.

With these types of samples being saved for future investigative cases, the teeth recovered from the boy's brain have been sent to a pathologist, Beaty said.

The report is published in the Feb. 27 issue of the New England Journal of Medicine, LiveScience reported.