It is rather like cancer. Hens are the only animal on the planet who get spontaneous ovarian cancers tumors/cancers like human women. I've found in medical journals where they are studying chicken hens to learn about female cancers. Hatchery stock is by no means the only types who get this ailment, a reproductive malfunction more than a disease in my opinion, but I do think that being bred exclusively for egg laying rather than having attention paid to health and longevity does contribute to it somewhat. It's one reason I don't add artificial light to make mine lay when they should be slowing down or taking a break.