What percentage of solid testicle lumps turn out to be cancer?

If you have already been through an ultrasound and they found a solid mass on the testicle what percentage of those solid masses statistically turn out to be a cancerous tumor as opposed to benign? I would love it if someone could link to a source as well. Someone in a TC forum stated that 95% of solid masses turn out to be cancer. I have not been able to verify this anywhere.