She's the Brisbane grandmother who has taken her fight against a multinational biotechnology company to the highest court in the land.

Yvonne D'Arcy, 69, of Logan, near Brisbane, went to the High Court on Tuesday for the latest chapter in her David and Goliath struggle with medical diagnostics firm Myriad Genetics.

Yvonne D'arcy says no company should be able to patent genetic material. Credit:Peter Rae

When she attended her first hearing in the case five years ago, in the Federal Court in Sydney, she wore a wig to hide her hair loss from chemotherapy for a second bout of breast cancer.

On Tuesday, she came to Canberra with a healthy head of hair, having gone five years without treatment. On Friday, she will have a mammogram to determine whether she remains cancer free.