One of my hold back females has developed a large marble sized lump on her throat. I don't know when it first appeared but it is now very noticeable and I feel it must have developed quickly. There is no sign of any injury that would have formed an abscess, though I suppose it could be inside the throat. I'm not taking it to a vet and I suspect I won't be criticized here for it. If she shows signs of pain I will put her down. My sister is a vet and can help me determine specifically what it is.

What she probably can't answer is this: Is this a heritable trait? Should I assume the offspring of this pairing are more prone to tumors? If the tumor does not kill her, should I avoid breeding this rat or does it not matter?