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CANINE MELANOMA |
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CANINE MELANOMA |
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Melanoma tumors in dogs, more
than most cancers, demand immediate attention. As a group,
melanomas can be either benign or malignant. Early recognition
of melanomas can lead to more successful attempts at removal and identification
of the grade or stage of cancer. The risk of metastasis for benign
forms of melanoma is not very high but these can be locally invasive.
Malignant melanomas can metastasize (spread) to any area of the body especially
the lymph nodes and lungs and present very challenging and dangerous prospects
for the dog. Cats seem much less susceptible to melanoma tumors than
dogs.
Some dog breeds are more at risk for melanomas such as those below:
Airedales Boston Terrier Boxer Chihuahua Chow Chow Cocker Spaniel
Doberman Golden Retriever
Irish Setter Miniature Schnauzer Scottish Terrier Springer Spaniel
BENIGN MELANOMAS...
Benign cutaneous melanomas of dogs are usually seen as round, firm,
raised, darkly pigmented masses from one-quarter to 2 inches in diameter.
They occur most often on the head, digits or back.
MALIGNANT MELANOMAS...
In the dog, presence of malignant melanoma may be first discovered
in the lungs where diffuse pulmonary infiltration of tumors will be displayed
throughout the lung tissue on a radiograph (x-ray). Lymph node swelling
or enlargement may be a clinical sign of malignant spread of a melanoma.
Some melanomas do not display the characteristic darkly pigmented color
of most melanomas. The pigment called melanin is a hallmark of these
tumors and usually is present in large amounts in melanomas.
DIAGNOSIS...
A definitive diagnosis is made via microscopic analysis (histopathology
evaluation by a Specialist in Veterinary Pathology) of a small section
of the growth. This is called a "biopsy" of the tumor. The
examining pathologist usually will grade the specimen according to how
actively the cells are replicating. This gives an approximation of
how likely the growth is to invade and spread. If an entire growth
is removed, the pathologist can report on the tissue's grade as well as
any evidence that parts of the tumor may not have been thoroughly excised
by the surgeon.
TREATMENT...
Treatment of melanomas is best provided by surgical excision of the
tumor and nearby surrounding tissue. Localized tumors may be completely
removed and the patient cured. However, if a malignant melanoma has
had the opportunity to spread to distant areas of the body, long term survival
of the dog is not likely. Chemotherapy has been performed with marginal
success; complete remissions of metastatic melanoma cases are rare.
Fortunately most cutaneous (skin) melanomas are benign, but individual
growths need to be evaluated as unique and unpredictable since any given
melanoma may become malignant.
Case Presentation:
A Golden Retriever was presented for routine vaccinations. The
attending veterinarian, as part of the pre-vaccination physical exam, noticed
an abnormal, darkly pigmented, raised tissue mass at the lateral edge
or the dog's right corneal-scleral junction. The suspicious mass
was creating a slight deviation in the smooth surface of the cornea and
seemed to be invading both the sclera (white area of the eye ball) and
the cornea. Because the veterinarian suspected the mass was a melanoma,
referral to a specialist in Veterinary Ophthalmology was done. Dr.
Sam Vainisi of the Animal Eye Clinic in Denmark, Wisconsin, evaluated the
four-year-old Golden Retriever and suggested that surgery be done.
Using a CO2 laser the growth was excised. Because of the depth and
diameter of the growth, as well as the unusual location, Dr. Vainisi performed
a frozen tissue, cornel-scleral graft with healthy tissue from the clinic's
eye bank to fill in the defect. The tissue graft was carefully sutured into
the surgical site. Topical and oral antibiotics and an anti-inflammatory
medication were used after the surgery and healing of the surgical site was
uneventful. The photos below display the melanoma prior to the surgery
and six months after. Annie, the patient, is healthy and active and
is expected to have no visual impairment as a consequence of the tumor.
Thanks to the specialist's careful evaluation and surgical excision of
this melanoma, Annie is expected to have no further problems with the eye.
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BENIGN
MELANOMA OF THE EYE IN A DOG
(click on an image
to see close-up view) |
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| Two views of a dark, raised mass of six
month's duration at the corneoscleral junction in a Golden Retriever |
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| Two views of the healed surgical site,
six months after surgical excision and with tissue transposition |
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If you discover a darkly pigmented,
raised, thickened growth anywhere on your dog, be sure to have your veterinarian
evaluate it. Keep in mind that pigmented (black) areas of the skin
are common in dogs and cats, especially in the tongue, gum and eyelid tissues...
and these darkened areas may be completely normal for that individual.
However, if any darkly pigmented areas are actually raised above the normal
surface or seem thickened or ulcerated or inflamed, an exam is indicated.
