Cancer & Tumors

  • Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body (such as the nasal cavity, ribs, etc.). Chondrosarcoma is the second most common primary bone tumor in dogs. Canine chondrosarcoma most commonly affects the flat bones of the body, such as the ribs, skull, nasal cavity and pelvis, although the limbs can also be affected. Aggressive surgical resection is typically recommended, although radiation therapy may also be used (depending on location). Metastasis may occur, but is relatively uncommon.

  • A cutaneous histiocytoma is a common benign (harmless) tumor of the skin in dogs, typically younger ones. Their development, appearance, diagnosis, and treatment are explained in this handout.

  • Cutaneous histiocytosis is an uncommon condition in dogs. It is a non-cancerous increase in the number of reactive cells (histiocytes) caused by an immune system dysfunction. It generally manifests as multiple bumps and nodules confined to the dog's skin. The clinical signs, diagnosis, and treatment of this condition are explained in this handout.

  • Skin cancers are common in cats, but cutaneous lymphoma is relatively uncommon. Less than 2% of lymphoma cases in cats occur in the skin. As the disease progresses, the skin becomes thickened, reddened, ulcerated, and may ooze fluid. The most common locations to find lesions include the junction between mucus membranes and the skin. Unfortunately, feline cutaneous lymphoma is considered incurable. Surgical removal can be attempted for solitary lesions, although the tumor often returns to the area or will have spread elsewhere in the body already

  • Systemic lymphoma is a very common cancer in dogs, but the cutaneous form is quite rare. Current statistics suggest that cutaneous lymphoma accounts for only about 5% of canine lymphoma cases. The disease can present in a variety of lesions, including ulcers, nodules, red patches, and areas of hair loss and skin scaling. Because not very much is known about canine cutaneous lymphoma, there are no standard treatment protocols and the prognosis is poor.

  • Collecting tissue samples for cytology or histopathology allow a pathologist to often give a diagnosis of the type of mass or tumor your pet has. Samples can be obtained by fine needle aspirate or biopsy, where a piece of the mass is cut out. Based on what the mass appears like under the microscope, the pathologist can often give a prognosis of how the tumor will behave.

  • Ear canal tumors are abnormal growths that can develop from any part of the ear canal (the skin, the glands of the skin that produce earwax and oil, and the underlying connective tissues, muscles, and bones). Initially, these tumors may appear as one or more pink, white, or purple nodular masses in the ear canal. If benign, they may grow to a certain size and may or may not be problematic. If malignant, they may grow, ulcerate (break open) and bleed, and nearly always become infected, causing recurrent or chronic ear infections. The treatment of choice for ear canal tumors is surgical excision.

  • Esophageal tumors are extremely rare but more often than not malignant type tumors. The cause is unknown but cases in tropical environments may be due to infection by the worm Spirocerca lupi. Treatment options are limited as surgical complications are high due to the advanced nature of the disease at time of diagnosis.

  • Eye melanomas in cats may be benign or malignant (cancerous). Malignant tumors, called diffuse iris melanomas, show up as multiple spots of color change in the iris, while benign tumors, called limbal melanomas, present as a distinct mass at the edge of the cornea. The diagnosis of these tumors is largely by clinical signs and tumor appearance. Treatment for diffuse iris melanomas may include close monitoring, laser surgery, removing part of the iris (iridectomy) and removing the eye (enucleation). Metastasis has been reported in about 19-70% of cases of diffuse iris melanoma, with most spread to the regional lymph nodes, kidneys, liver, and lungs. Treatment for limbal melanomas may include close monitoring, and surgery, sometimes combined with cryosurgery, laser surgery, or radiation therapy. Enucleation is an option if the treatment is unsuccessful, or the tumor regrows.

  • Eye melanomas, although rare, are the most common eye tumor in dogs. These melanomas can originate from the uvea (structures in the front part of the eye) or the limbus (the part where the cornea and the white part of the eye meet). About 80% of uveal melanomas and all limbal melanomas are benign. The rate of metastasis (spread to other parts of the body) is less than 20%. Ocular melanomas are at least in part heritable and may caused by one or more genetic mutations. Uveal melanomas can become discrete, raised pigmented masses that damage the intraocular structures of the eye and cause hyphema (blood in the front part of the eye), uveitis (inflammation of the front part of the eye), and glaucoma (increased pressure in the eye). Limbal melanomas can invade the cornea and cause keratitis (inflamed cornea), grow outwards and cause conjunctivitis, and penetrate and damage the eye as with uveal tumors. Treatment for ocular melanomas may include close monitoring, surgery, iridectomy (removal of part of the iris), laser surgery, cryotherapy, radiation therapy, and enucleation (removing the eye), depending on the type and size of the tumor and how it is affecting the eye. The overall prognosis is good.