Hi, these researchers in Sweden trained dogs to distinguish ovarian carcinomas from healthy control tissue samples. They found that:
Using our training method, we taught a dog to distinguish different histopathological types and grades of ovarian carcinomas, including borderline tumors, from healthy control samples. Double-blind tests showed 100% sensitivity and 97.5% specificity. Moreover, the odor of ovarian carcinomas seems to differ from those of other gynecological malignances such cervical, endometrial, and vulvar carcinomas. Our study strongly suggests that the most common ovarian carcinomas are characterized by a single specific odor.
Source:
Integrative Cancer Therapies 2008 Jun;7(2):76-80. Epub 2008 May 27.
Possibly this has been done with breast cancer as well!