How are skin tumors diagnosed in dogs?

Skin tumors can be alarming when detected in a dog. Tumors, in general, are usually associated with malignancy and cancer and create a stigma and fear among dog owners. However, some tumors are considered harmless and often do not cause any health problems. Proper identification and diagnosis of the tumor are necessary to know if treatment or any sort of intervention is needed.

Identification of the tumor involves getting a representative tissue sample from the tumor. There are different ways to obtain samples from a tumor, ranging from non-invasive procedures to methods that require anesthesia or sedation. The most common method to obtain a sample from a skin tumor is through fine-needle aspiration (FNA). The downside of fine-needle aspiration procedure is there is a chance of a non-definitive diagnosis if the cells obtained are not truly representative of the tumor.

Other options for diagnosing skin tumors involve removing a piece or taking out the whole tumor for identification. Both of which would require general anesthesia and pain management to be able to properly perform.

Common Types of Skin Tumors Found in Dogs

1. Mast Cell Tumors

Most mast cell tumor cases in dogs are found on the skin, but some can originate from internal organs. Considered one of the most common tumors in dogs, mast cells tumors are mainly composed of a particular type of immune cell called mast cells. Normally, mast cells are located in different parts of the body and play an important role in allergic reactions in dogs. They contain chemical granules that trigger an allergic reaction and inflammatory response when released, which happens when the animal is exposed to a certain allergen.

Diagnosis of mast cell tumors (MCT) can be done through fine-needle aspiration. The presence and abundance of mast cells from the obtained sample is often definitive of mast cell tumor. Recommended treatment is the surgical removal of the tumor, using a wide-margin excision technique which includes taking out a portion of the healthy tissue or skin to prevent or reduce chances of regrowth.

For mast cell tumors that are inoperable due to their location, or if complete removal is difficult to achieve, chemotherapy and radiation are often indicated.

2. Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is a rare form of skin cancer but the most frequently encountered carcinoma in dogs. SCC tumors are often seen in older dogs, and breeds like Basset Hounds, Beagles, and Standards Poodles are at a greater risk of developing it. SCC in dogs appears as raised, ulcerated plaques and nodules on the skin of the animal. This type of tumor can grow into a large mass if not dealt with immediately.

Recommended treatment is the surgical removal of the primary tumor. A wide margin incision during surgery will reduce the risk of tumor regrowth. Dogs with incompletely removed tumors can undergo radiation therapy to prevent regrowth. SCC can invade local lymph nodes and metastasize into other organs such as the lungs, liver, and kidneys, which can lead to more serious health problems.

3. Melanoma

Melanomas are skin tumors arising from the pigmented cells of the dog’s skin. This type of tumor happens more often in breeds with dark skin. Most melanoma tumors are benign and do not metastasize or spread to other parts of the dog’s body. Malignant melanomas, though quite rare, do occur and are often highly invasive and aggressive. Immediate medical treatment is indicated once a malignant melanoma is identified or diagnosed in dogs.

Surgical removal of benign skin melanomas is often curative in dogs, and the chances of regrowth are very slim. In malignant melanomas, however, chemotherapy coupled with immunotherapy is often needed even after the successful removal of the tumor.

4. Lipomas

Lipomas are another commonly found tumor on a canine’s skin. This type of tumor is often found around the animal’s trunk or legs. Certain breeds like Labrador Retrievers and Miniature Schnauzers are at a greater risk of developing lipoma tumors. Diagnosis can be done through a fine-needle aspirate. Lipomas are considered to be the easiest tumor to identify as the samples obtained during biopsy procedures will have a distinct oil-like texture and appearance.

For most dogs with lipomas, the tumor is confined within the skin and subcutaneous layer and does not cause serious health problems. Surgical removal is the ideal treatment, but in cases where the tumor is not too big and doesn’t cause any discomfort to the animal, leaving it alone is also an option.

There are rare cases where lipoma tumors infiltrate the underlying muscle fibers, making surgical removal complicated. These types of lipomas are called infiltrative lipomas, usually located on the chest and legs, and are most commonly seen in middle-aged female dogs. Doberman Pinschers, Labrador Retrievers, and mixed-breed dogs are at a greater risk of developing infiltrative lipomas. The recommended treatment for infiltrative lipomas is still surgical removal, but a healthy part of the affected tissue must be removed as well to prevent regrowth.

Read more:

Histiocytomas in Dogs

Warning Signs of Cancer in Dogs

Mammary Tumors in Dogs

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