Ten-year-old Hannah Powell-Auslam said she's trying to remain brave as she battles an extremely rare, adult form of breast cancer that led to a mastectomy.

"I feel like a kid inside but sometimes I feel like an adult, when I'm always at the hospital," Hannah told ABC's "Good Morning America" in an interview that aired Wednesday. "I'm a kid fighting an adult disease."

The fifth-grader at Escalona Elementary School in this Los Angeles bedroom community complained of itching in her side in April. Her mother discovered a lump, and that led to a diagnosis of breast cancer — an extremely rare adult form.

Click here to read more about Hannah's story.

Hannah had a mastectomy May 7 and has begun several rounds of chemotherapy.

"You feel like you're sick all the time. You just want to go lay in bed," she said.

The show filmed Hannah at home getting her head shaved rather than waiting for chemotherapy to take its toll. Other family members got buzz cuts, too, in solidarity.

"I might be just a little bit afraid. I love my hair. I worked so hard to grow it," Hannah said before the event.

Asked if she felt brave, Hannah nodded firmly.

"Feel brave all the time," she said.

After her haircut, the event became a giggly party as Hannah tried on new hats.