Cronulla prop Johnny Mannah will undergo treatment for lymphoma after a biopsy on his troubled back returned a positive result for the condition.

The Sharks released a statement on Thursday addressing the 19-year-old's health and said Mannah would begin treatment next week.

Lymphoma is a type of cancer that affects the immune system.

"The Sharks can confirm that a biopsy result for Johnny Mannah has come back positive for lymphoma, with Johnny to begin treatment next week," the statement said.

"At this stage the club is unable to make further comment or give more detail.

"We would request that the privacy of Johnny and his family is respected while he attempts to deal with this condition and begin his recovery."

Johnny's older brother Tim Mannah, 21, plays with Parramatta, where the pair played Toyota Cup together.

Australian schoolboys representative Johnny moved to the Sharks from the Eels at the start of the season to seek more first grade opportunities, and still lives with his brother in the family home in Sydney's south-west.

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