Because cats experience a wide range of cancer types and each case is unique, this blog provides an overview of common cancers by breed, as well as insights into two cancers common in cats.
Cancer Predispositions by Breed
Siamese cats can have higher rates of mammary, intestinal, and mast cell tumors and sometimes develop cancer at younger ages than other breeds. Persian cats can be more prone to basal cell tumors and have a higher risk of sebaceous gland tumors and skin cancers. Maine Coons can have higher rates of hip dysplasia, which can lead to bone cancer. They also tend to be more susceptible to lymphoma and spinal cord tumors. All light-colored cats can be more susceptible to squamous cell carcinoma, especially if they have pink noses or ears or areas of unpigmented skin.
Other factors related to all breeds include age, as cats 10 years or older have higher cancer risks. Female cats have a higher risk of mammary tumors and larger breeds tend to get bone cancers more often.
Feline Mammary Carcinoma
Mammary carcinoma, or breast cancer, is the third most common type of cancer in cats and its behavior can mimic human breast cancer. Mammary carcinoma often starts in one of the abdominal glands and can spread quickly. Cats often have several masses. Unfortunately, this is an aggressive cancer, with 90% of tumors being malignant and between 50-90% of them metastasizing.
Cats with mammary carcinoma are staged 1-4, with stage 1 being a mass <2 cm and no systemic spread, and stage 4 having distant metastases. Metastasis means the disease has spread; therefore, the overall survival time is lower. The size of the mass when it first presents also provides important information about expected prognosis. For example, if the mass is >3 cm, the cancer is likely more aggressive.
Surgical removal of the mass is the mainstay of therapy. Radical mastectomy, or the removal of all of the mammary chain on one or both sides of the patient, is the attempt to remove all cancer that might be present or prevent more from forming. Chemotherapy is then often recommended to help destroy any remaining microscopic disease and those cancer cells that want to spread or metastasize. Palliative mass removal, which is surgically removing only the tumor that is present, can extend a patient’s life by a substantial amount, provided there is no disseminated disease.
Chemotherapy, which is generally well tolerated in cats, is then used to try to slow down recurrence or metastasis. Radiation may also be recommended after surgery if good margins cannot be achieved. A specially-trained oncologist and radiation oncologist can help determine the best treatment protocol. Survival times vary based on the size of the tumor, evidence of metastasis, and the treatment options chosen.
Feline Lung Tumors
Lung tumors are often classified as primary (originating in the lung) or metastatic (originating from a different part of the body and spreading to the lung). Primary lung tumors in cats are generally rare, and the most common types of tumors that originate in this location are adenocarcinomas. Other less common types of cancer in this region include sarcomas and squamous cell carcinoma. In tumors that originate in the lungs, there is potential for spread to other parts of the body, including bones, lymph nodes, and muscles.
Prior to beginning therapy, staging tests may be recommended to determine the extent of cancer spread. A CT scan is often needed prior to surgery for planning and to help determine if there is any spread or metastasis to other lungs or regional lymph nodes. An abdominal ultrasound is often performed to rule out a different cancer that may have spread to the lungs.
Feline lung tumors have been shown to have a variety of paraneoplastic syndromes, or a secondary effect due to the cancer. Paraneoplastic syndromes that have been documented include elevated calcium, lameness from lung-digit syndrome, and laryngeal paralysis. Lung-digit syndrome is when nodules on the toes and a lung mass are present, a condition that is documented in both cats and people. Unfortunately, the prognosis with cats that have lung-digit syndrome is very poor. Surgical removal of the affected toes or limbs has not been shown to provide successful palliative care as additional nodules tend to quickly develop.
If there is no evidence of cancer spread, the treatment of choice for these types of tumors is surgical removal of the lung mass. The prognosis depends on the biopsy, which is obtained from surgical removal of the mass. Tumors that are well-differentiated (in which the cancer cells appear more like normal cells) tend to have a better prognosis, with average survival times of approximately 698 days. Tumors that are poorly differentiated (in which the cancer cells do not resemble normal cells), or in cases where there is cancer spread elsewhere, unfortunately, carry a poorer prognosis, with average survival times of 75 days. For those cases with metastasis or the tumor inoperable, chemotherapy may be indicated. Early detection and an evaluation by a board-certified veterinary oncologist will help determine the best treatment options for each individual cat’s unique case.
