What’s That Black Spot on My Pet’s Skin?

The skin is an amazing part of the body. It is the first line of defense against infection and contains a number of specialized cells that produce hair, form the oil glands and the sweat glands. In addition there are tissue cells that help the body withstand and repair itself from day to day trauma that occurs with sun, heat, and cold exposure, abrasions, cuts and bruises and other trauma. Just like people, dogs and cats have pigments and freckles in the skin that can vary with their coat color, their breed, and the location on the body. And they are at risk for skin growths.

Champ is our Pet of the Month for April because he highlights the importance of investigating skin growths quickly. Champ is my own dog. He is a 9 year old Labrador Retriever who comes to work with me every day. Champ was adopted from a shelter three and a half years ago and came to us with ‘issues’ – he has separation anxiety, panics with thunder, and he can jump out of our tallest dog runs – so he spends his day in my office or with employees when they have time to give him belly rubs. One of the benefits of being Champ is that there are a lot of eyes paying attention to him on a regular basis!

A few weeks ago, despite all of this regular attention, it was surprising to suddenly find a raised black growth on Champ’s belly near one of his nipples. It literally seemed like this growth appeared overnight. It was about the size of a grain of rice, black and slightly raised above the surface of the skin. A pigment spot or freckle can be various shades of light to dark but they are always flat to the skin surface. Dogs don’t typically get moles like people, so immediately I was concerned about Melanoma. Two days later I took him to surgery. The biopsy report confirmed that this small little black tissue was a melanoma. Champ was fortunate that the location on his body allowed a wide surgical margin of normal skin around the cancerous tissue and his prognosis is likely very good.

Melanomas:

• Melanomas can occur anywhere on the body including in the mouth, on the top of the nose, in the eye, around nail beds; anywhere pigment cells are present.
• There may be a genetic component to melanomas in dogs as certain breeds have a higher incidence.
• Melanomas that involve the mouth and nail beds are more commonly malignant and can be difficult to surgically excise completely.
• Despite their name, not all melanomas are black – some are amelanotic melanomas which can appear like normal skin, or may be red, pink, purple.
• Not all melanomas are cancerous – some can be considered benign and surgical excision is curative.
• Malignant melanomas can metastasize to distant parts of the body – lymph nodes and lung or liver being most common.
• Survival times depend on the exact nature of the tumor, how successfully it has been removed, which part of the body, and follow-up treatments.

Fortunately there are some encouraging developments for canine patients. The Michigan State Melanona Prognositc Panel uses special testing methods to classify and predict how a particular tumor will behave. In consultation with a veterinary oncologist, this test can help determine how malignant a particular tumor is, and provide information to assist with treatment planning, In addition, the Canine Melanoma Vaccine, which utilizes DNA Immunotherapy, can be used to treat patients who have been diagnosed with Malignant Melanomas and substantially improve their survival.

At Hawthorne Hills Veterinary Hospital we encourage you to be proactive in addressing any lump or bump on the skin or under the skin that your pet may develop. This means getting an exam early, having the tissue evaluated either with a Fine Needle Aspirate or surgical excision and getting a definitive answer. There are many growths that are benign, but if it turns out to be cancerous, early intervention helps provide the best possible outcome.

Links:

• http://wearethecure.org/learn-more-about-canince-cancer/canine-cancer-library/melanoma-melanocytic-tumors/
• https://www.vet.upenn.edu/docs/default-source/ryan/oncology-handouts/melanoma.pdf?sfvrsn=4
• http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=2941
• http://www.petcancervaccine.com/Pages/default.aspx

Robin E. Riedinger, DVM Hawthorne Hills Veterinary Hospital, Seattle WA | bumps and skin masses, Diagnosis, Lumps and Skin Masses, Surgical Conditions