Mast Cell Tumor (Mastocytoma) in Dogs

Mast cells are cells that reside in the connective tissue, specifically those vessels and nerves closest to external surfaces such as the skin, lungs, nose and mouth. Their primary function includes defense against parasitic infestations, tissue repair and the formation of new blood vessels. They can also be associated with allergic reactions.

Mast cell tumors (mastocytomas) in dogs are graded according to their location in the skin, their presence of inflammation and how well they are differentiated.

• Grade 1 cells - well differentiated with low potential for metastasis.
• Grade 2 cells - intermediately differentiated with potential for locally invasive metastasis.
• Grade 3 cells - poorly differentiated or undifferentiated with high potential for metastasis.

There are four stages of the disease which includes:

• Stage 1 - single tumor, no metastasis.
• Stage 2 - single tumor with metastasis into the surrounding lymph nodes.
• Stage 3 - multiple skin tumors, or a large tumor that has invaded subcutaneously.
• Stage 4 - presence of a tumor, with metastasis to an organ or widespread mast cell presence in blood.

The image below of a canine mast cell tumor was captured with a biological microscope using the Lumenera Infinity 2-2 microscopy camera. The prepared slide was stained with a toluidine blue stain.

Canine Mast Cell Tumor with Toluidine Blue Staining (C) Lumenera