Michael Strahan's 19-year-old daughter, Isabella Strahan, is battling a brain tumor. The dad and daughter duo shared the news together on Thursday in a joint interview with Robin Roberts for Good Morning America. 

The announcement comes nearly two months after the 52-year-old GMA co-host made his return to the ABC morning show and to his NFL analyst job for Fox NFL after a mysterious weeks-long absence. 

"I literally think that in a lot of ways, I'm the luckiest man in the world because I've got an amazing daughter," Michael tells Roberts in the new interview. "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."

Isabella reveals that she first began suffering symptoms in early October, just as she was beginning her freshman year at the University of Southern California, when she "noticed headaches, nausea, couldn't walk straight." Eventually, things reached a turning point when she woke up "throwing up blood." At that point, Isabella says, she "notified the whole family." 

Michael says the family urged Isabella to "go get a thorough checkup" at that time. 

"And thank goodness for the doctor," he adds. "I feel like this doctor saved her life because she was thorough enough to say, 'Let's do the full checkup.'" 

Isabella's health check included an electrocardiogram (EKG) and Magnetic resonance imaging (MRI). From there, she was rushed to Cedars-Sinai Medical Center in Los Angeles, California, where doctors discovered a fast-growing four-centimeter tumor -- larger than a golf ball -- in the back of her brain. The malignant brain tumor is known as medulloblastoma. 

Michael reveals that he received the news before Isabella did, and that "it didn't feel real." He then traveled to California to be by her side as she underwent emergency surgery to have the mass removed. The procedure was done on Oct. 27, one day before Isabella's 19th birthday. 

According to estimates published in the Journal of Clinical Neuroscience, Medulloblastoma accounts for about 20 percent of all childhood brain tumors with about 500 children diagnosed each year. 

Isabella appears in good spirits during the interview, wearing a pink coat and jeans while rocking a shaved head, revealing that she has already undergone a month of rehabilitation and completed six weeks of radiation treatment. Following her surgery, she learned to walk again with the help of her twin sister, Sophia Strahan. 

Michael shares the twins with his ex-wife, Jean Muggli. He is also dad to Tanita Strahan, 32, and Michael Strahan Jr., 29, whom he shares with his first wife, Wanda Hutchins. 

Looking to the future, Isabella is set to begin chemotherapy at Duke Children's Hospital & Health Center in Durham, North Carolina. As part of her journey, she's launching a new YouTube series to help the hospital. 

"It's been like, two months of keeping it quiet, which is definitely difficult," she says. "I don't wanna hide it anymore 'cause it's hard to always keep in. I hope to just kind of be a voice, and be [someone] who people, maybe [those who] are going through chemotherapy or radiation can look at."

For his part, Michael says that the experience has been a humbling lesson in perspective. 

"You learn that you're probably not as strong as you thought you were when you have to really think about the real things, and I realized that I need support from everybody," he explains. "You think that I'm the athlete, the tough guy, you know, I can come and handle, I'm the father in the family. It is not about any of that. It doesn't matter. And it's really made me change my perspective on so many things in my life."

"Perspective is a big thing," Isabella adds. "I'm grateful. I am grateful just to walk or see friends or do something, 'cause when you can't do something, it like, really impacts you."

She notes that she's "feeling good, not too bad," these days.

"And I'm very excited for this whole process to wrap," she continues. "But you just have to keep living every day, I think, through the whole thing." 

She also has her sights set on a return to school. 

"I'm looking forward to getting back to college and moving back to California and just starting my school experience over," she shares. "Not over, but just restarting, being back into a routine and something that's enjoyable."

At the time of Michael's sudden absence from GMA, a spokesperson told ET that the former New York Giants player was "dealing with some personal family matters." 

"Michael is a huge presence at GMA, and his absence is definitely felt," the source added. "He's universally adored. Everyone wishes him the best as he deals with personal family matters. The hope is for him to get back to work soon."

Just last summer, the proud dad happily praised his daughters as they graduated from high school. In his tribute to Isabella, he called her "intelligent, beautiful and hard-working." 

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