(CNN) On bad days, Dewayne Johnson is too crippled to speak. Lesions often cover as much as 80% of his body.

Doctors have said they didn't expect him to live to see this day. But Monday marks a milestone: Johnson, 46, is the first of hundreds of cancer patients to see his case against agrochemical giant Monsanto go to trial.

Johnson, a former school groundskeeper, regularly used Roundup and claims it gave him cancer.

CNN reported last year that more than 800 patients were suing Monsanto , claiming its popular weed killer, Roundup, gave them cancer.

Since then, hundreds more non-Hodgkin's lymphoma patients have made similar claims, Johnson's attorney, Timothy Litzenburg, said. He now represents "more than 2,000 non-Hodgkin's lymphoma sufferers who used Roundup extensively," he said.

Johnson, a father of two in California's Bay Area, applied Roundup weed killer 20 to 30 times per year while working as a pest manager for a county school system, his attorney said.