The Infestation infects all fish on Deimos, even those that do not show any external mutations. Source: Cut from all Cambion Drift fish via Daughter in the Necralisk (Deimos).
Stats
Type
Fish Part
Not in the current drop tables (may come from crafting, in-game market, bounties or special content).
FAQ
Can Benign Infested Tumor be traded?
No, Benign Infested Tumor cannot be traded: you have to earn it in-game.