Mary K. Klein, DVM, MS, DACVIM, DACVR (radiation oncology)

Mast cell tumors are the most commonly encountered malignant skin tumor in the dog. They account for 16-21% of all cutaneous tumors and boxers, Boston terriers, Labrador retrievers, beagles and schnauzers are documented to be at increased risk. Alterations in the c-kit receptor (receptor for growth factor SCF) are noted in many high grade tumors. Histologic grade is highly predictive of behavior.

This is the most common reason for presentation to the emergency clinic in patients currently undergoing chemotherapy. Any chemotherapy patient that is not feeling well should have a CBC performed, as well as a thorough physical examination.

Canine lymphoma comprises approximately 7-24% of all canine neoplasia and 83% of canine hematopoietic malignancies. This translates to ~24/100,000 dogs at risk and is one of the most commonly treated malignancies both in the private practice and specialty setting.

Oral tumors account for ~6% of canine tumors making them the fourth most common neoplasm in that species. Four major histologic classifications; fibrosarcoma, melanosarcoma, squamous cell carcinoma and the epulides account for the vast majority of cases. Other less common diagnoses include lingual tumors, tonsillar SCC, viral papillomatosis, eosinophilic granuloma complex and papillary squamous cell carcinoma of young dogs.

Radiation therapy is one of the most powerful tools available in the fight against cancer and can be applied as a primary treatment modality, in combination with surgery and/or chemotherapy in an adjuvant setting, or as a palliative therapy. The dose of radiation therapy administered is limited by the tolerance of normal tissue structures within the treatment field.

Molecular biology and genomic profiling now enable the identification of specific targets within cancer cells. Selectively designing therapies to interfere with those targets allows the treatment to become more 'personalized' as it is based on the targets identified in that patient's tumor cells.

The information gained from the pathologist can be invaluable and should be maximized at every opportunity. The pathologist's job is to determine 1) tumor vs. no tumor 2) malignant vs. benign 3) tissue of origin 4) margins in excisional specimens and 5) a histologic grade when available.