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.
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.
Intestinal tumors are uncommon in dogs and cats. There are many kinds, including leiomyosarcomas, lymphomas, adenocarcinomas, mast cell tumors, GISTs, plasmacytomas, carcinoids, and osteosarcomas (all malignant) and leiomyomas, adenomatous polyps, and adenomas (all benign). Most intestinal tumors are malignant. Intestinal tumors are more prevalent in older animals, males, and certain breeds. The signs of intestinal tumors vary according to the area of the intestinal tract that is affected, and can include vomiting, lack of appetite, lethargy and weight loss for the upper bowel and difficulty defecating, ribbon-like stools, and rectal prolapse with the lower bowel. Sometimes tumor ulceration causes anemia. Paraneoplastic syndromes are possible with the muscle tumors. Intestinal tumors may be diagnosed with imaging, endoscopy, or surgery, with a biopsy. Treatment may involve surgery, chemotherapy, or radiation therapy.
Primary liver tumors in dogs and cats are rare. There are 4 types: hepatocellular tumors, bile duct tumors, neuroendocrine tumors, and sarcomas. These cancers can be massive, nodular, or diffuse in form. In dogs, most liver tumors are malignant, while in cats, most are benign. The signs of liver tumors range from being asymptomatic to having inappetence, fever, lethargy, and weight loss; and less commonly, nausea, vomiting and diarrhea; increased drinking and urination; and jaundice. Occasionally there are neurological signs, such as seizures. With tumor rupture and intrabdominal bleeding there may be weakness, collapse, and difficulty breathing. The diagnosis is based on history, clinical signs, exam findings, diagnostic imaging, and FNA or liver biopsy. A biopsy is best for a definitive diagnosis. Surgery is the treatment of choice for most primary liver tumors followed by chemotherapy. Chemoembolization is a newer treatment.
Lung tumors are considered rare in cats and dogs. Certain breeds are more predisposed to develop pulmonary tumors than others. Not all pets with pulmonary tumors exhibit clinical signs and are often diagnosed incidentally from routine chest X-rays. Ultrasound-guided fine needle aspiration or biopsy will confirm the diagnosis. Pulmonary carcinomas have a high tendency to metastasize, so full staging is recommended. Surgery is by far the most common treatment, though radiation therapy may be considered if surgery is not possible.