Histiocytoma in Dogs
A histiocytoma is a benign skin tumor that originates in the Langerhans cells, immune cells that function to provide protective immunity to the tissues that are in contact with the outer environment — the nose, stomach, intestines and lungs, but mainly the skin’s surface. These cells are also referred to as dendritic cells, and histiocytes.
Histiocytomas are common in dogs, with some breeds appearing to be more predisposed that others. These breeds include flat-coated retrievers, bull terriers, boxers, dachshunds, cocker spaniels, Great Danes, and Shetland sheepdogs. More than 50 percent of diagnosed patients are under two years of age. Otherwise, there is no gender difference.
– Small, firm, dome or button-shaped masses on the skin surface
– Rare autoimmune blistering (dermoepithelial) masses, which may be ulcerated
– Fast growing, nonpainful, usually solitary
– Common sites are the head, ear edges, and limbs
– Occasionally multiple skin nodules or plaques
You will need to give a thorough history of your dog’s health and onset of symptoms, after which your veterinarian will perform a thorough physical exam. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, a urinalysis and an electrolyte panel. Most of these tests return as normal.
Other diagnostic tests include a cytologic examination (a microscopic examination of the cells) using a sample gathered by fine-needle aspirate. This may reveal pleomorphic round cells (cells taking one or more forms), with variable-sized and -shaped nuclei. It is common to find that the mitotic index (a measure of the proliferation, or fast production status of a cell population) is high. The tests may also show evidence of substantial lymphocyte (white blood cell in the vertebrate immune system), plasma cell, and neutrophil (the most abundant type of white blood cells) infiltration.
What is Surgical Tumor Removal ?
The word tumor refers to an abnormal growth of cells that results in a lump forming. However, tumors range widely in significance from harmless growths (described as ‘benign’) to aggressive life-threatening lumps that seed cancer cells to other parts of the body (described as ‘malignant’). For many lumps, it is best to err on the side of caution and treat them early, so as to reduce the risks should they be malignant. Depending on the type of tumor, the options include surgical removal, chemotherapy, or radiation treatment. Of these, surgical removal is by far the most widely performed and common in first opinion practice.
Efficacy of Surgical Tumor Removal in Dogs
The success of surgery depends on:
– The type of tumor
– How early the tumor was caught
– How much tissue was removed from around the tumor
– Surgical technique
For small benign masses, surgery will be curative. When possible, the lump should be sent away for analysis. This not only confirms what type of tumor was present, but checks that ‘clean margins’ were obtained, meaning that enough tissue was removed to reasonably assume the cancer has been eliminated from that area. For large malignant masses, the surgery may not be curative but may ‘debulk’ the tumor and buy the patient some extra time. For many patients, the outlook is good, especially with prior screening to check for complications ahead of surgery. Incomplete removal of an invasive tumor can mean it recurs.
Surgical Tumor Removal Recovery in Dogs
An average, recovery time from surgery is 10 – 14 days for straightforward cases. During this time the dog must be prevented from licking the operation site by wearing a cone or having the area covered with a dressing. The dog must avoid exertion, which could burst the stitches, and only go on gentle lead walks (as instructed by the vet). Internal stitches dissolve of their own accord but those in the skin will be removed at 10 – 14 days. Once the results of the lab report are known, the vet will decide if further action is needed. This may include regularly screening to look for recurrence, or further treatments such as chemotherapy or radiotherapy.
Dogs and Skin Cancer
You might not give much thought to dog skin cancer, because your loyal companion is covered with hair and protected from the sun. But you should know that skin tumors, which may be cancerous, are the most common tumors found in dogs. Fortunately, when caught early, many cases of dog skin cancer can be treated successfully.
Not all varieties of dog skin cancer are caused by sun exposure, but sun damage to the skin can be a factor. All dogs have certain areas, such as the nose and the ears, where there is no or little hair to shield sensitive skin from the sun. Additionally, pooches with light-colored or thin coats are more susceptible to sun damage over their entire bodies.
Because some types of dog skin cancer, including dog melanomas and mast cell tumors, are fatal if untreated , it is important that you have your veterinarian check any suspicious growths.
Types of Skin Cancer in Dogs
There are different types of dog skin cancers. Three of the most common include:
1. Malignant melanoma.
Just as in people, malignant melanoma is a type of skin cancer in dogs that affects pigmented cells known as melanocytes. Dogs often develop benign tumors in pigmented cells that do not metastasize, which are called melanocytomas. These tumors are found on areas of the dog’s body that have hair.
Most malignant melanomas occur on the mouth or mucous membranes, although about 10% of the time they are found on parts of the body covered with hair. They tend to grow extremely fast and are likely to spread to other organs, including the lungs and liver.
No one knows exactly why melanomas develop, although genetic factors seem to play a role. Additionally, trauma or compulsive licking of a particular spot on the skin may increase the likelihood that cells will multiply, thereby raising the chances that cells will mutate during the division process and become cancerous.
2. Squamous cell carcinoma.
This form of dog skin cancer, which occurs in the skin, is often caused by exposure to the sun. Scientists believe there may also be a connection between the papilloma virus and the development of squamous cell tumors in certain dogs.
Although squamous cell cancers do not spread to surrounding lymph nodes, they are aggressive and may lead to destruction of much of the tissue around the tumor.
3. Mast cell tumors.
These dog skin cancers, which occur in the mast cells of the immune system, are the most common skin tumors in canines. Veterinarians don’t know what causes mast cell tumors to develop, although there have been cases where they have been linked to inflammation or irritants on the skin. Evidence suggests genetic factors are often important, and the hormones estrogen and progesterone may also affect cancer growth.