Educational Articles

Dogs + Tumors

  • 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.

  • 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.

  • Cytology is the microscopic examination of cell samples. Cytology can be used to diagnose growths or masses found on the surface of the body, and also to assess bodily fluids, internal organs, and abnormal fluids that may accumulate, especially in the chest and abdomen. Cells can be collected using various methods including fine needle aspiration, skin scraping, impression smear, cotton-tipped swabs, or lavage. A biopsy is the surgical removal of a representative sample of tissue from a suspicious lesion. The most common biopsy techniques are punch biopsy, wedge biopsy, and excision biopsy. The tissue is then processed and is examined under a microscope via histopathology. Histopathology allows the veterinary pathologist to make a diagnosis, classify the tumor, and predict the course of the disease.

  • 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 in dogs and cats. There are many kinds, including squamous cell carcinomas, leiomyosarcomas, fibrosarcomas, osteosarcomas, and undifferentiated sarcomas (all malignant); and leiomyomas and plasmacytomas (benign). Most tumors are malignant. These tumors occur mostly in the upper esophagus in cats and the lower esophagus in dogs. In dogs, most cases of esophageal sarcoma are associated with spirocercosis. Esophageal cancer causes progressive signs of regurgitation, difficulty swallowing, excessive salivation, weight loss, and lack of appetite. It is diagnosed with imaging, endoscopic or surgical biopsy, and histopathology. Surgery is a treatment option, with the possibility of radiation therapy for tumors of the upper esophagus. Avermectins may be used with benign spirocercosis. Palliative care may be possible with the placement of a feeding tube.

  • Ocular melanomas, although rare, are the most common eye tumor in dogs. Ocular melanomas can originate from the uvea or the limbus. About 80% of uveal melanomas (and all limbal melanomas) are benign. The rate of metastasis is less than 5%. Ocular melanomas are at least in part heritable and 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, uveitis, and glaucoma. Limbal melanomas can invade the cornea and cause keratitis, 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, laser surgery, cryotherapy, radiation therapy, and enucleation, depending on the type and size of the tumor and how it is affecting the eye. All tissues removed should be sent for histopathology for a definitive diagnosis. The overall prognosis is good.

  • Primary intraocular tumors, aside from melanoma, are relatively uncommon. There are many different types of primary tumors, including ciliary body adenoma and adenocarcinomas, uveal schwannomas of blue-eyed dogs, feline post-traumatic ocular sarcomas, and iridociliary adenomas and adenocarcinomas. When an intraocular tumor is suspected, a referral to a veterinary ophthalmologist may be recommended. Diagnosis is usually via an abnormal ophthalmic examination and/or ophthalmic ultrasound. Surgery is often recommended, especially if the pet has symptoms that reduce quality of life. The risk of metastasis is related to the type of tumor.

  • There are a number of tumors that affect the eyelids, conjunctiva, and periocular tissues. These can be benign or malignant and can lead to secondary problems such as eye infections and corneal ulcerations. Diagnosis is best achieved through complete surgical excision of the tumor, but fine needle aspiration may be pursued as an initial diagnostic. Surgery is highly recommended to provide the pet with symptomatic relief, remove the tumor, and obtain a definitive diagnosis. With malignant tumors, surgery is the mainstay of therapy, though radiation therapy is sometimes pursued in cases where surgical removal is not possible.

  • Fibrosarcomas are a type of soft tissue sarcoma that is common in dogs. They are most often found on the limbs and trunk of the body, but can also be found in the nasal cavity or mouth. They usually originate from the connective tissue of the skin and beneath the skin, but occasionally from the bone, causing a primary form of bone cancer. Older dogs and certain breeds (especially large breeds) are at greater risk. The clinical signs vary in relation to the size and location of the tumor, and its impact on the surrounding tissues. Fibrosarcomas are often painful. The diagnosis is most often based on tissue biopsy. Surgery is the treatment of choice for fibrosarcomas, with or without radiation and/or chemotherapy. Most tumors recur after surgery because of the degree of local invasiveness. Only about 10% of fibrosarcomas metastasize. With proper and prompt treatment, favorable outcomes are possible.