Peripheral odontogenic fibroma (formerly known as fibromatous and ossifying epulis) is a benign, often slow-growing tumor that arises from periodontal structures. They can be further sub-classified as peripheral odontogenic fibromas and acanthomatus ameloblastomas. These tumors do not spread to other organs; however, extension to surrounding tissues is common. Treatment is dependent on size and location of the tumor. If surgery cannot be performed, radiation therapy is an excellent alternative for ameloblastomas given their high degree of response to radiation therapy.
Oral squamous cell carcinomas (SCC) are the most common oral tumor in cats, and second most common in dogs. These tumors are locally aggressive, with a possibility to metastasize. Regardless of the location of SCC, surgery is the typically the standard treatment. Radiation therapy may be recommended following surgery or as a primary treatment for palliative care. Staging is recommended for all cases. If metastasis is present chemotherapy is often pursued.
Osteosarcomas are somewhat rare in cats and progress slowly. Osteosarcoma is very painful. The most common location where osteosarcomas develop in cats is the hindlimb. Amputation is by far the most common treatment. Chemotherapy is not generally pursued without evidence of metastasis, given the relatively long-term control with surgery alone.
Ovarian tumors are quite rare in North American pets, mainly due to routine spaying practices. Several types of tumors can arise from the tissues of the ovary. How the tumor will affect your pet is entirely dependent on the location and type of tumor. By far, ovarian cancer is most commonly diagnosed by abdominal ultrasound or during a spay procedure. Full staging is recommended prior to surgery to determine if the cancer has metastasized. Treatment for solitary masses without evidence of spread typically involves ovariohysterectomy. If metastasis is present, chemotherapy should be considered, however its efficacy is not completely known. Without evidence of spread, ovarian tumors carry a good prognosis.
Primary pancreatic tumors are rare in dogs and cats. Exocrine tumors include adenomas and adenocarcinomas, and endocrine tumors include insulinomas, gastrinomas, and glucagonomas. Insulinomas are the most common type of pancreatic tumor, followed by adenocarcinomas. Both tumors are more common in dogs than cats. Large breed dogs and Siamese cats may be predisposed. Insulinomas are usually diagnosed with the finding of hypoglycemia with normal to high insulin on bloodwork and concomitant clinical signs. Adenocarcinomas typically go undetected until the clinical signs of metastasis are evident. For both tumors, diagnostic imaging and exploratory surgery with tumor removal (or biopsy) and histopathology are needed for a definitive diagnosis. Insulinomas can be treated with surgery and chemotherapy. Surgery is possible with adenocarcinomas, but as the cancer is more diffuse and has usually metastasized by the time of diagnosis, the prognosis is poorer. Chemotherapy and radiation therapy are ineffective in the treatment of adenocarcinomas. Given the high rate of metastasis with these tumors, staging is recommended prior to surgery.
Parathyroid tumors are uncommon in dogs and cats. Benign adenomas occur more often than malignant tumors. Keeshonds appear to have a genetic predisposition to developing parathyroid tumors, however no breed or genetic relationship has been established in cats. Pets may exhibit signs of lethargy, little or no appetite, vomiting, and muscle twitching. Diagnosis is confirmed with PTH testing and ultrasound of the neck region after hypercalcemia is observed on bloodwork. Surgery to remove the affect gland(s) is the typical treatment, however ultrasound-guided ablation may be pursued. Careful monitoring of calcium levels post-surgery is important, as some pets may develop a transient hypocalcemia and require calcium supplementation. Prognosis is excellent, and the metastatic rate for these tumors is extremely low.
Clinical signs of pituitary tumors depend on whether the tumor is functional or nonfunctional. Functional tumors can cause Cushing’s disease in dogs, and both acromegaly and insulin-resistant diabetes in cats. Nonfunctional pituitary tumors can enlarge to cause neurological signs. Diagnosis may be based on the history, bloodwork, urinalysis, and sometimes a CT scan or MRI. Medical therapy is often the treatment of choice for functional tumors. Radiation therapy is another option and is usually the primary treatment for nonfunctional tumors.
Plasma cell tumors develop as a result of dysregulated production of plasma cells and are relatively uncommon in dogs and cats. Some plasma cell tumors are benign and are typically confined to the skin or oral cavity, and most are very treatable. Surgical excision is the treatment of choice for removal of benign plasma cell tumors, with little to no recurrence if completely excised. Conversely, multiple myeloma is an aggressive cancer that is usually treated with chemotherapy.
Tumors of the prostate are relatively uncommon in dogs and extremely rare in cats. The most common tumor is prostatic adenocarcinoma. Clinical signs include blood in the urine, changes in urination habits, or straining to urinate or defecate. Metastasis to the pelvic bone and/or lumbar spine is likely. FNA of the prostate aids in the diagnosis, though surgical biopsy may need to be considered. Treatment is limited. Stents may be placed in patients with tumors obstructing the urethra. Radiation therapy in conjunction with NSAID therapy has shown significant survival advantage when compared to pets who did not receive NSAID therapy. The role and/or benefit of chemotherapy is not well understood.
Radiation therapy is the medical use of high dose radiation to destroy cancer cells by damaging the cells’ DNA to interfere with cell replication and kill them. It may be used on its own or in combination with other treatments, such as surgery or chemotherapy, or to reduce the size of very large tumors prior to surgery. There are several radiation protocols used in veterinary medicine. Your veterinary oncologist will choose the therapy most appropriate for your pet’s individual situation.