Like I said, it was a friend's fish and he no longer has it. It ate well and was otherwise healthy except for a large jet black blotch on the lower side of the fish that looked like an inkblot.
What tipped us off to look into melanoma was that I remembered reading that livebearers such as swordtails with black markings were considered to have cancer...especially if the black radiated into the fins. Interestingly, I'm told that if the black is only on the body like Berlin swordtails then that is considered benign. As opposed to if the black spread into the fins. Although it is confusing why red wag swords are considered okay. Where did you have the biopsy done?