The phrase "atypical cases" refers to situations or examples that are not typical or normal. It describes situations that are unusual, uncommon, or different from what is usually expected. Full definition
After weeks of testing and treatments, the vets discovered that she had a very atypical case of intestinal lymphoma and went downhill very quickly. (neogreyhound.com)
An exome sequencing study of Moebius syndrome including atypical cases reveals an individual with CFEOM3A and amutation. (mendelian.org)
Experts generally agree that BSE is most likely spread when cattle are fed meat and bone meal that contains brain or spinal cord from an infected animal, although recent atypical cases in the US suggest that more research is needed in this area. (oregonvma.org)