Neuroendocrine tumors are a group of tumors that develop from the cells of the neuroendocrine system, and include insulinomas, gastrinomas, glucagonomas, carcinoids, medullary thyroid carcinomas, small-cell lung carcinomas, pheochromocytomas, chemodectomas, and Merkel cell carcinomas. Some of these tumors are functional, while others are non-functional. The signs of disease in dogs and cats depend on the type of growth, location of the tumor, its size, the degree of infiltration in the surrounding tissues, whether it has metastasized, and whether it is functional. A definitive diagnosis requires tissue biopsy and histopathology, often with histochemical staining and electron microscopy. Staging is highly recommended for these tumors. Treatment may involve surgery, chemotherapy, radiation therapy, and medical and dietary management.

Nasal tumors are an uncommon type of cancer but when they do occur, they tend to be malignant and locally aggressive. Staging can be done to determine the type of cancer and if it has affected anywhere else in the body. Treatment can be done in some cases to help relieve clinical signs, most often with radiation therapy.

Many herding breeds (most commonly Collies and Australian Shepherds) have a mutation at the MDR1 gene that makes them more sensitive to the negative effects of certain medications. These drugs include several antiparasitic agents (when given at high doses), the antidiarrheal agent loperamide (Imodium®), and several anticancer drugs. The effects of the mutation vary in severity, depending on whether the dog carries one or two copies of the mutation. There is a cheek swab or a commercially-available test that assesses blood samples for the presence of the MDR1 mutation.

Melanomas are cancerous growths of the cells responsible for pigmentation of the skin. They can develop anywhere on the body but those on the toes carry the highest chance for malignancy. They may be painful and you may notice your pet licking at the affected area. Surgery is often the treatment of choice and may be followed up with radiation or chemotherapy.

Mast cell tumors are most common in the skin of dogs and may appear red, ulcerated, or swollen. They can be itchy and can fluctuate in size. Tumors can range from lower-grade, with minimal spread, to higher-grade, with a high risk of local invasion. Treatment usually involves surgical removal and may require supportive treatment including chemotherapy, radiation therapy, and therapy to target the mutation that instigated the tumor.