It has been already published in May this year, but I think it is still worth mentioning here:
Bloomberg (klick on the link to see the orginal article) reports that dogs can be trained to sniff whether a person has breast cancer or prostate cancer. The selectivity, by which dogs discriminate between positive and negative samples is 90% and more. If we could train our dogs to do so, all mamma screening e.g. would become obsolete. We do not know what substances the dogs smell, but we can envisage that once they are identified we could train enough dogs to do the job or analytical chemistry might be able to do so. One would hope that dogs will be used because the test would be ultimately cheaper and emotionally closer than in the case of chemistry.