Dog nail melanoma, also known as subungual melanoma, may not be straightforward to recognize. Knowing how dog nail melanoma looks like may therefore be important considering that many cancers in dogs have a better prognosis when they are detected at an early stage. Knowledge is ultimately power. Veterinarian Dr. Ivana Crnec discusses the signs of nail melanoma in dogs, what it looks like, including diagnosis, treatment and prognosis of affected dogs.
Melanomas in Dogs
Melanoma is a skin tumor that affects the melanocytes. Melanocytes are skin cells responsible for pigment production. In humans, most melanomas are malignant, while in dogs, most are benign. However there are certain exceptions.
Melanomas can develop in different locations and their exact biological behavior depends on that location. Generally speaking, in dogs, there are four different types of melanomas. Let's take a closer look at them.
Oral Melanoma – this is the most common type of melanoma in dogs. Oral melanomas in dogs may occur in many different places such as the lip, tongue, hard palate, soft palate or gingiva. Oral melanomas are more frequently seen in older dogs (above 10 years of age) and in dogs belonging to smaller breeds (Miniature Poodles and Cocker Spaniels).
Oral melanomas tend to behave differently in different cases – they can be dark pigmented or pinkish, can occur solitary and superficially or invade the surrounding soft tissues and deeper structures such as bone and they ultimately can grow as a mass or appear as a flat lesion.
Oral melanomas are quite aggressive and tend to metastasize the local lymph nodes, and in more severe cases, even the lungs. Therefore removing the oral tumor is not enough.
Nail Bed (Subungual) Melanoma – this is the second most common type of canine melanoma. The exact location of the tumor is the subungual crest, formally known as the nailbed.
This type of tumor occurs as a solitary mass. Affected dogs show lameness and the affected toe tends to swell and bleed.
Nailbed melanomas have a relatively high metastatic rate and tend to invade the closest lymph nodes. If the melanoma is on the front foot, the metastasis are on the axillary and superficial cervical lymph nodes. If the melanoma is on the hind foot, the metastasis are on the popliteal lymph nodes.
Dermal Melanoma – this type of tumor presents as intensely pigmented mass on the skin. The mass can occur at one or more places. Dermal melanomas are quite invasive and can even protrude under the skin in which case are commonly known as subcutaneous melanomas.
In 85 to 90 percent of cases, dermal melanomas occurring on haired skin are benign and therefore the treatment of choice is surgical removal.
Dermal melanomas occurring on muco-cutaneous junctions such as lip margin, anus or vulva have much more aggressive behavior and are usually classified and treated as malignant.
Ocular melanoma – this tumor can affect several ocular structures such as conjunctiva, uvea and eyelid. On the bright side most ocular melanomas in dogs are benign. However, they tend to grow, and as they enlarge, they start to cause problems.
What Does Dog Nail Melanoma Look Like?
Digital tumors in dogs are fairly common. According to reports, around 17 percent of all digital tumors are classified as nail bed melanomas. Sadly, nail bed melanomas have extremely high metastatic rates and at the time of diagnosis, one-third of patients will show signs of lung metastasis.
What does melanoma of the dog's nail bed look like? Dogs with a nail bed melanoma will have a dark brown or black colored mass on the toe.
This lump is the most common and most obvious sign. The swelling can vary, but in most cases it is significant enough to cause lameness. The toe may bleed or produce puss or some other type of discharge.
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Upon initial examination, the nail bed melanoma may be mistaken for an infected toe. This is because the symptoms are identical – there is swelling, redness and pain upon touch. In such cases, antibiotics are given, but normally they cannot resolve the problem.
Depending on the exact stage of presentation, the dog’s lymph nodes around the affected area may be significantly enlarged. If the condition is progressed and the tumor has already affected the lungs, respiratory clinical signs can be observed.
Such signs may include coughing and difficulty breathing. In extremely advanced cases, poor appetite, weight loss and malaise will be present.
At the Vet's Office
Regardless of the location, melanomas in dogs are diagnosed based on fine needle biopsy or regular tissue biopsy. The collected samples are properly prepared and subjected to microscopic evaluation.
To evaluate the dog’s overall health, it is advisable to perform blood tests and urine testing. The blood test should include a complete blood count as well as a chemistry profile.
Once these parameters are tested, the vet will be able to evaluate the dog’s internal organs and determine whether anesthesia and surgery are safe and possible. To determine the presence of metastasis the vet will likely suggest performing a chest x-ray and abdominal ultrasound.
It is also advisable to evaluate the lymph nodes surrounding the tumor area. Fine needle biopsy is a great way of determining the spread of the tumor. However, in some cases, it is necessary to have the entire lymph node removed and microscopically analyzed. If the lymph nodes are properly evaluated and the tumor’s spread is well-determined it will be easier to determine the course of the treatment.
The treatment for nail bed melanoma in dogs is complex, and, more often than not, requires a multi-modal approach.
The first step is surgical removal of the tumor. To ensure better outcome it is essential to have the entire toe removed. Surgical amputation of the toe is necessary to achieve local disease control.
The second step is chemotherapy. Usually, patients require one chemotherapy treatment every three weeks. The total number of treatments varies between four and six. It should be noted that some patients tolerate the chemotherapy medication better than others. Transient but mild side-effects can always be expected.
The next step is radiation therapy. Radiation therapy can either prevent or significantly delay the onset of melanoma regrowth. Radiation therapy is usually initiated two weeks after the surgical tumor removal and it usually involves six to seven treatments. It should be noted that to administer the radiation treatment, the patient needs to be sedated or anesthetized.
Ultimately, there is a so-called melanoma vaccine that helps the body neutralize any residual tumor cells.
What the prognosis of nail bed cancer in dogs? The prognosis ultimately depends on the condition’s stage as well as on the treatment’s prompt and proper onset.
About the Author
Dr. Ivana Crnec is a graduate of the University Sv. Kliment Ohridski’s Faculty of Veterinary Medicine in Bitola, Republic of Macedonia. She currently practices as a veterinarian in Bitola and is completing her postgraduate studies in the Pathology of Domestic Carnivores at the Faculty of Veterinary Medicine in Zagreb, Croatia.
Ivana’s research has been published in international journals, and she regularly attends international veterinary conferences.