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Personal Story: Dogs: Companions, hunters, and cancer detectors?

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Can dogs sniff out cancer?    Resources            


“Shannen Doherty Opens Up About Chemo Struggles Through Picture of Her Beloved Dog That Sniffed Out Her Cancer.” This title appeared with an article that People magazine published this past August about the Beverly Hills, 90210 actress Shannen Doherty and her dog. The Huffington Post, US Magazine, and Entertainment Tonight also ran similar stories about how her dog was able to smell her cancer.

The report raises the following issue:

Has research been done on dogs smelling cancer?

“The notion that animals, especially those with a highly sensitive sense of smell, such as dogs, can sniff malignant tumors is nothing but awkward,” writes Giuseppe Lippi and Gianfranco Cervellin in their scientific review of canine olfaction (smell) detection of cancer. Shannen Doherty claims that her dog obsessively sniffed at her right side, where her breast cancer was subsequently discovered. Other similar cases dating back to 1989 have been published in the literature as case reports, which are scientific publications based on observations of a single patient.

Other studies have tried to determine whether dogs that are trained to recognize the “scent” of a cancer can correctly sniff out the cancer samples from noncancer samples. There are not many of these studies, and the success of the findings differs by cancer type, but some of the results suggest that dogs, with their extremely sensitive sense of smell, are picking up on something that is being emitted from some of the cancer samples.

Does this mean dogs can reliably sniff out cancer?

Not at all.

This is an interesting field of study that has potential to aid in developing new technologies for cancer detection—the dogs may smell odors that humans can’t detect. These odors might be new biomarkers for a particular cancer, and once they are identified, humans can try to develop technologies that are specific for that . However, there is not sufficient data to definitively say that dogs are able to sniff out cancers. Because of this, headlines like the one about Shannen Doherty’s dog are more of an interesting story than a medical finding.

While a few published case studies that sound similar to Shannen Doherty’s story have been published, there is a tendency in academic science to only publish positive results. What this means is that positive things such as a dog sniffing out a cancer are more likely to be published than dogs sniffing at something that is not cancer.

People can look for established signs if they are concerned about breast cancer. Women should be familiar with the look and feel of their breasts, and notice any changes. The Susan G. Komen website notes the following symptoms:

  • A lump, hard knot or thickening inside the breast or armpit
  • Any swelling, warmth, redness or darkening of the breast
  • Any changes in size or shape of the breast
  • Any dimpling or puckering of the breast skin
  • itchiness, or a scaly sore or rash on the nipple
  • A nipple pulling inwards
  • Nipple discharge that suddenly appears
  • Any new pains in the breast that don’t go away

While these changes do not indicate that a person has breast cancer, they indicate the need to see a health care provider to get it checked out.  Men also get breast cancer, although at far lower rates than women. They may notice similar changes and should take similar action if they do.


Stories about cancer-sniffing dogs are interesting and could lead to some really cool biological discoveries. But they are not clinically applicable for human patients—people can look to their furry friends for companionship, but not for cancer screening.

Posted 9/6/16


Lippi G. and Cervellin G. “Canine olfactory detection of cancer versus laboratory testing: myth or opportunity?” Clin Chem Lab Med, 2012; 50(3): 435-439.

Warning Signs of Breast Cancer” from Susan G Komen.

This article is relevant for:

This article is also relevant for:

people with breast cancer

healthy people with average cancer risk

men with breast cancer

people with a genetic mutation linked to cancer risk


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Expert Guidelines
Expert Guidelines

The National Comprehensive Cancer Network breast screening guidelines recommend the following for women at average risk for breast cancer: 

  • ages 25-39: 
    • practice breast awareness
    • clinical breast exam every 1-3 years
    • risk assessment, including questions about family and personal medical history, should be done during clinical exams to find high-risk women who may need additional screening
  • ages 40 and older:
    • practice breast awareness
    • yearly clinical breast exam
    • risk assessment, including questions about family and personal medical history, should be done during clinical exams to find high-risk women who may need additional screening
    • yearly  –consider a , if available. 
  • The NCCN has a different set of guidelines for individuals who are  at increased risk for breast cancer.

Many other professional societies and organizations have breast cancer screening guidelines that differ slightly. They don't all agree on the starting age and frequency of screenings.

It is important to note, that all of the groups support the opportunity for women ages 40 to 49 to decide whether screening is right for them.

Updated: 02/05/2022

Questions To Ask Your Doctor
Questions To Ask Your Doctor

  • What are things I can do to lower my breast cancer risk?
  • Can you help me assess my breast cancer risk?
  • What factors would put me at high risk of breast cancer?
  • What types of changes in my breast should I be concerned about?
  • How often should I have regular breast cancer screening?

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