Cancer

Cancer is a progressive disorder that permanently alters your cat's stats and genetics after each battle. At the end of every battle, you lose 3 random stats permanently and gain a random mutation. Mutations typically provide +2 to one stat and -1 to another, so the net effect of Cancer is a gradual reshuffling of your cat's stats, losing 3 stats while gaining a mutation that gives +2 and -1. Over many battles, Cancer slowly degrades your cat's total stat pool.

Cancer is heritable and can pass from parent to kitten through breeding. It can also be acquired through events or applied with a Disorder Syringe from the Organ Grinder. Compared to Tainted Genes, which also grants post-battle mutations but without stat loss, Cancer is the worse version since the 3 random stat loss significantly outweighs the +2/-1 from the mutation. The mutation gain provides some variety and occasional useful effects, but the net result is a cat that gets weaker over time.

Cancer should be replaced as soon as possible due to its cumulative negative impact. Every battle makes your cat slightly worse, and in long adventures this degradation becomes severe. If you want mutation accumulation without the stat drain, Tainted Genes is the superior alternative. The only potential silver lining is that specific mutations might provide useful passive effects beyond their stat changes, but this does not compensate for the guaranteed stat loss. Prioritize getting Cancer removed or replaced in any serious run.