02/24/2014 04:09 am ET Updated Feb 24, 2014

Jake 'The Snake' Roberts: I Have Cancer

Daniel Boczarski via Getty Images

Jake "The Snake" Roberts has a cancerous tumor behind his knee ... and the wrestler says it's slowly growing into his muscle -- so he needs emergency surgery to remove the growth.

Roberts tells TMZ ... he noticed a tumor behind his knee the size of a half dollar last month so he had it tested ... and on Friday doctors told him the test came back positive for cancer.

Read more on TMZ