Michael Strahan and his daughter, Isabella Strahan, appeared on “Good Morning America” Thursday to share her brain tumor diagnosis.

Isabella Strahan was diagnosed with a type of malignant brain tumor known as medulloblastoma last October after starting to experience serious headaches about a month into her first semester at the University of Southern California in Los Angeles. She was 18 at the time.

“I didn’t notice anything was off until probably, like Oct. 1,” Isabella Strahan told Robin Roberts of her symptoms. “That’s when I definitely noticed headaches, nausea, couldn’t walk straight.”

Though she first thought she was dealing with vertigo, the now 19-year-old knew there was something much more serious going on when she woke up vomiting blood on Oct. 25, several weeks after the headaches began.

After symptoms persisted, Isabella Strahan decided to go to doctors, who discovered a fast-growing tumor at the back of her brain. The tumor measured 4 centimeters — larger than a golf ball.

Michael Strahan told “GMA” that learning of his daughter’s diagnosis felt surreal.

“I don’t really remember much,” he said. “I just remember trying to figure out how to get to LA ASAP. And it just doesn’t feel real.”

Days after her diagnosis, Isabella Strahan underwent emergency surgery at Cedars-Sinai Medical Center in LA.

Her treatment continued with a month of rehabilitation, followed by six weeks of radiation therapy. She is set to begin chemotherapy at Duke Children’s Hospital & Health Center in Durham, North Carolina, next month.

“That’s my next step. I’m ready for it to start and be one day closer to being over,” Isabella Strahan said.

Michael Strahan said his daughter has been a pillar of strength during her treatment, telling Roberts, “I literally think that in a lot of ways, I’m the luckiest man in the world because I’ve got an amazing daughter.”

“I know she’s going through it, but I know that we’re never given more than we can handle and that she is going to crush this,” he said.