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.
The histiocyte group of cells are part of the body's immune surveillance system. They take up and process foreign antigens, such as pollens and viral, bacterial and fungal microorganisms.
Skin cancers are fairly common in cats, but cutaneous lymphoma is quite uncommon. Only about 3% of lymphoma cases in cats occur in the skin. There may be a linkage between feline leukemia virus (FeLV) and feline cutaneous lymphoma. Unfortunately, feline cutaneous lymphoma is considered incurable.
Systemic lymphoma is a very common cancer in dogs, but the cutaneous form is actually quite rare. Current statistics suggest that cutaneous lymphoma accounts for only about 5% of canine lymphoma cases.
The histiocyte group of cells are part of the body's immune surveillance system. Cutaneous (reactive) histiocytosis is an uncommon condition of dogs. Cutaneous, reactive histiocytosis is an immune dysfunction, mainly of young dogs and probably due to persistent antigenic stimulation by a variety of antigens (foreign proteins).
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 can be benign or malignant. Diagnosis is typically via fine needle aspiration or tissue biopsy. The treatment of choice for ear canal tumors is surgical excision. For benign tumors, complete surgical removal is curative. With malignant tumors, a CT scan is often performed prior to surgery to determine how invasive the tumor is and enable surgical planning. Total ear canal ablation and bulla osteotomy (TECA-BO) is the most common surgical option. Radiation therapy or chemotherapy may be pursued.
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 in cats may be benign or malignant. Malignant tumors, called diffuse iris melanomas, present as multifocal iridial pigmentation, and benign tumors, called limbal melanomas, present as a discernable limbal mass. The diagnosis of these tumors is in large part by clinical signs and tumor appearance. Treatment for diffuse iris melanomas may include close monitoring, laser surgery, iridectomy, and enucleation. As some iris melanomas progress slowly (over years) intervention may not be required for some time. Metastasis has been reported in about 60% of cases of diffuse iris melanoma, with spread most commonly to the regional lymph nodes, kidneys, liver, and lungs, but unlike other cancers, metastatic disease may not become evident for years. Treatment for limbal melanomas may include close monitoring, and surgery (with or without grafting) sometimes combined with cryosurgery, laser surgery, or radiation therapy. Enucleation is an option if the treatment is unsuccessful or the tumor regrows. Histopathology is always recommended for a definitive diagnosis.
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.