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Michael Strahan and his daughter Isabella revealed her brain cancer diagnosis was the reason for his mysterious absence last year.

Isabella, 19, shared her brain cancer diagnosis during an emotional segment on GMA with Strahan and co-host Robin Roberts on Thursday.

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The USC freshman began experiencing intense migraine headaches in September. She also suffered waves of nausea and had difficulty walking straight.

In late October, Isabella told her sister she was throwing up blood. She was seen by neuro specialists at Cedars Sinai Medical Center in Los Angeles.

They discovered “a fast-growing, four-centimeter tumor” in the cerebellum at the back of Isabella’s head.

The cerebellum controls walking, coordination, balance and a sense of equilibrium.

“I don’t really remember much,” said Strahan. “I just remember trying to figure out how to get to L.A., ASAP. It just doesn’t feel real.”

He eventually returned – first on “Fox NFL Sunday” on Nov. 12, and then to GMA on Nov. 15.

“It’s great to be back,” he said, without revealing any details about his absence.

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Isabella (right) underwent brain surgery to remove the tumor in October, followed by six weeks of radiation therapy.

She received chemotherapy treatments at Duke University, where her twin sister Sophia (left) is a freshman.

“I’m feeling good, not too bad. I’m very excited for this whole process to wrap but you just have to keep living every day through the whole thing,” Isabella said.

“With my platform, I hope to just kind of be a voice and be a person who people who maybe are going through something similar, going through chemotherapy or radiation, can look at and just hear and just watch, or find something interesting about their day,” she said. “I’m just excited for that.”

“This is something that is so personal,” Michael told Roberts, a breast cancer survivor.

“But her idea was, ‘I want to share it and I want to help other people,’ and that goes into the spirit of who she’s always been.”

In addition to Sophia, Isabella is sister to half siblings Tanita and Michael Jr.

Isabella and Sophia are Michael’s daughters by his ex-wife Jean Muggli.