When to perform immunohistochemistry on biopsy samples, and why.
Diagnosis and treatment of feline small cell lymphoma: 2020 update.
Ann Hohenhaus, DVM
Diplomate, ACVIM (Oncology and Small Animal Internal Medicine)
Staff doctor, Department of Oncology, Animal Medical Center, NY, NY USA
An accurate diagnosis is critical to cancer patient management. Most often, the diagnosis of a tumor is made based on histopathology of a biopsy specimen. Based on the location of the tumor and microscopic features, the pathologist creates a list of differential diagnoses and then narrows down the list to a final diagnosis, based on the appearance of the cells and stroma. If the tumor retains the morphologic features of normal tissue, the diagnosis is straight forward. If the biopsy sample demonstrates overlapping features between more than one tumor type or if the tumor appears to be highly unusual for the tissue of origin, immunohistochemistry (IHC) can be helpful for differentiation and confirmation of the final diagnosis. Results of IHC are helpful in allowing the pet owner to have a better understanding of their pet’s prognosis and the veterinarian to choose the most efficacious treatment. This presentation will use actual patient biopsy information to demonstrate the clinical utility of IHC in oncology patients.
In the feline leukemia virus (FeLV) era which occurred prior to the mid 1980’s, most lymphoma was found in young cats and involved the cranial mediastinum. With the advent of FeLV testing and vaccination programs, gastrointestinal lymphoma has become the most common form of feline lymphoma. This shift in anatomic form of feline lymphoma was noted around 2000, when several research publications identified a cluster of lymphoma in the small intestine composed of small lymphocytes infiltrating the intestinal wall. Histopathological analysis of biopsy material is required for diagnosis of small cell gastrointestinal lymphoma. This form of lymphoma is a slowly progressive disease. In most cases minimal treatment is required and results in prolonged survival. Most cats have one or more co-morbid diseases such as pancreatitis, heart disease and hyperthyroidism. Death is more commonly caused by one of the co-morbidities.
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