What is Canine Sarcoma? (National Canine Cancer Foundation)

This type of cancer begins in either the bone or in the body’s soft tissues. The word sarcoma is derived from a Greek word and means “fleshy growth”.  Sarcomas are a broad category of tumors classified together because of their similarities in their behavior and outcome.

• Sometimes further classification is made between bone sarcoma and soft tissue sarcoma.
• Generally, sarcomas are malignant tumors that affect the “connective tissues” in the body.
• The connective tissues may refer to nerves, blood vessels, bones, muscles, fat, cartilage, fibrous tissue or deep skin tissue.
• Sarcoma accounts for about 15% of canine cancers. It is most common in middle-aged and older dogs, especially large or giant breeds. (National Canine Cancer Foundation)

Where Soft Tissue Sarcoma in Dogs Occurs (Dog Cancer.com)

Soft tissue sarcoma, commonly abbreviated STS, is a broad term for tumors in soft and connective tissues.

Your dog’s body has many different soft and connective tissues. Some examples include:

• Muscles
• Blood and lymph vessels
• Nerves
• Tendons
• Fat
• Fascia (the thin layer of connective tissue that holds all of your dog’s bodily structures in place)

Soft tissue sarcoma can start as a single isolated tumor almost anywhere because soft and connective tissues are found throughout the body. Tumors are frequently given more specific names based on where the tumor started. Some examples include:

• Fibrosarcoma
• Histiocytic sarcoma
• Leiomyosarcoma
• Liposarcoma
• Myxosarcoma
• Peripheral nerve sheath tumor
• Perivascular wall tumors (hemangiopericytoma)
• Rhabdomyosarcoma

Some of these, such as liposarcoma and rhabdomyosarcoma, can vary as to whether they are clinically defined as soft tissue sarcomas. (Dog Cancer.com)

Types of Skin Cancer in Dogs (AKC)

There are several different types of skin cancer in dogs, just like there are several different layers of the skin. Each layer and skin component can develop distinct tumors, some of which may turn out to be cancerous.

Some of the more common types of skin cancer in dogs are:

• Malignant melanoma
• Mast cell tumors
• Squamous cell carcinoma
• Histiocytic cell tumors
• Fibrosarcoma

Malignant Melanoma

Melanomas can be either malignant or benign.

• These tumors are often dark-pigmented or can lack pigment. While benign melanomas are more common, malignant melanomas are a serious concern, as they grow quickly and have a high risk of metastasis (spreading to other organs).
• Malignant melanomas are most commonly found on the lips, mouth, and nail beds. According to some researchers, the head, neck and scrotum areas are also moderately predisposed to skin cancer.
• Certain breeds, for exampleMiniature and Standard Schnauzers and Scottish Terriers, are at an increased risk, and males appear to be affected more than females.
• Malignant melanomas look like raised lumps, often ulcerated, and can also look like gray or pink lumps in the mouth.
• Nail bed malignant melanomas, on the other hand, show up as toe swelling and possibly even loss of the toenail itself and destruction of underlying bone. Nail bed and footbed tumors often develop a secondary infection, leading to a misdiagnosis.
• These types of tumors usually metastasize to other parts of the body, decreasing the chances for a good outcome.

Mast Cell Tumors (Also see Lost Temple Pets Mast Cell Tumors)

Mast cell tumors are the most common types of skin cancer tumors.

• Mast cells release histamine, which is the chemical that causes some of the symptoms of allergic reactions in dogs, like irritation and itching.
• Mast cell tumors are cancers of these cells, and they can grow anywhere on your dog’s skin, as well as in internal organs.
• The most common sites for mast cell tumors are the limbs, lower abdomen, and chest.
• Boxers, Pugs, Rhodesian Ridgebacks, Boston Terriers and older mixed breed dogs seem particularly susceptible to mast cell tumors, which most commonly affect dogs ages 8-to-10 years old.
  • This cancer can be difficult to deal with, and your dog could have symptoms associated with toxins released from malignant mast cells, such as stomach ulcers, resulting from histamine release.

Squamous Cell Carcinoma

Skin squamous cell carcinoma is the most commonly diagnosed carcinoma of the skin, and primarily affects older dogs, especially Bloodhounds, Basset Hounds, and Standard Poodles.

• These tumors typically show up on the head, lower legs, rear, and abdomen, and appear as raised patches or lumps that are firm to the touch.
• Exposure to the sun can be a cause of squamous cell carcinoma, but according to the National Canine Cancer Foundation, “In dogs, the theory of exposure to sun is less obvious. It is believed that there may be some association with papilloma virus.”
• These tumors usually appear on your dog’s abdomen, which is the area least protected from the sun by hair.

Histiocytic Cell Tumors

Histiocytic cells are a type of skin cell. When these cells proliferate into tumors, they are classified as histiocytic cell tumors.

• These types of tumors are relatively common and typically affect dogs under 3 ¬Ω years old, especiallyScottish Terriers, Bulldogs, Greyhounds, Boxers, Boston Terriers, and Chinese Shar-Pei.
• There are three types of histiocytic cell tumors: histiocytomas, which are the most common; systemic histiocytosis, which mainly affects Bernese Mountain Dogs; and malignant histiocytosis, which also mainly affects Bernese Mountain Dogs and first shows up in the internal organs.

Fibrosarcoma

Fibrosarcoma and spindle cell tumors originate in the connective tissues of the skin and beneath the skin. These tumors can have a varied appearance, and while they are typically slow growing, they do tend to recur after surgical removal. Luckily, this type of tumor rarely metastasizes.

• Fibrosarcoma usually affects dogs when they are middle-aged or older, with an average age of 10 years.
• Sometimes, an aggressive type of fibrosarcoma can affect young dogs. Your veterinarian will send off a sample of the tumor to a pathologist to determine whether or not the tumor is a low- or high-grade tumor, a classification that refers to the rate of cell division. This will help them give your dog an accurate prognosis and determine the best course of treatment.
• This type of tumor is often found on the limbs.
• In addition to invading nearby structures, sometimes impeding their function, the tumors can also bleed, ulcerate, and become infected. (AKC)