As it turns out, not even naked mole rats are totally immune to cancer.

Researchers had never reported finding the deadly disease in the long-living rodents — not in the wild, or in zoos. Even after injecting their cells with the same viruses that trigger tumors in mice, the pink, wrinkly-skinned critters came out just fine. That is until earlier this month when a team of pathologists reported finding two cases of cancer in mole rats housed in zoos.

Does this cancel out the possibility that naked mole rats may hold a clue to fighting cancer? Not at all, said Martha Delaney, a veterinary pathologist at the University of Washington School of Medicine and lead author on the study, which was published in the journal Veterinary Pathology earlier this month. Rather, she said, these particular cases, one of glandular cancer and another of stomach cancer, may provide additional clues as to what makes mole rats so much less susceptible to cancer than other rodents and species with long life spans.

“Now that we have two naked mole rats with cancer,” she said in an email, “we can study the colonies from which they came to elucidate why they are cancer prone, compared to other zoo and research colonies.”

Dr. Delaney and her colleagues have studied lesions on naked mole rats for more than a decade, but it wasn’t until last fall when they came across their first cancerous case. Veterinarians from the Brookfield Zoo in Chicago sent the team a dark red and purple mass that was removed from the armpit of a 22-year-old male naked mole rat. Dr. Delaney’s team identified it as a malignant tumor and diagnosed adenocarcinoma, a type of cancer that develops from the body’s mucus-secreting glands, like the salivary glands or mammary glands.