Well, the longer you live, the more likely something will go wrong :-(!

Hoofprint Day Light Star will officially be 12 years and 6 months old tomorrow.  If you have a Q child or grandchild, you will want to take note of this information and add it to your charts.

Day has been diagnosed as having had 2 mast cell tumours. These tumours have been successfully removed and have been confirmed by histopathology.

Her tumours are a Grade II mast cell. This is a little worse than a Grade I, but although there is a 20% risk of these tumours regrowing, they are not likely to metastasize.

Causes/Predispositions: No one fully understands what causes cancer. Mast cell tumors are very common in dogs, yet they occur far less frequently in cats and very rarely in human beings. They occur in dogs of all breeds, ages, and genders and can occur anywhere on the body. There appears to be a genetic component, as certain breeds are predisposed to developing MCT.
Among the most common victims are beagles, Boston terriers, boxers, bulldogs, bullmastiffs, bull terriers, dachshunds, English setters, fox terriers, golden retrievers, Labrador retrievers, schnauzers, American staffordshire terriers, and weimaraners.

Boxers  are at the highest risk, yet mast cell tumors are often not as aggressive in this breed. There is some suggestion that mast cell tumor development may be associated with golden/red coat color and with chronic immune over-stimulation that occurs in dogs with allergies or other inflammatory conditions. There may be environmental factors, viruses, or other undetermined contributors. Mast cell tumors, as with all cancers, tend to be associated with age. Older dogs are more likely to develop cancerous growths, with the average age of a dog with MCT being 8-9 years.

I have edited out the parts of the following paper that pertain to cats

Mast Cell Tumors in Dogs and Cats
By Daniel A. Degner, DVM, Diplomate ACVS

What are mast cells?

Mast cells are normally found in the tissues of the body
A mast cell tumor is a mass of cancerous mast cells
They release histamine when stimulated.  Histamine causes signs of
allergies such hives. Histamine increases stomach acid production

Proteolytic enzymes released by mast cells delay healing of incisions.
Heparin, a blood thinning agent is also found in the mast cells.
Below is a photo of a fine needle aspirate biopsy of a mast cell tumor
as seen under a microscope; take note of the round mast cells that are
filled with purple granules which contain histamine and proteolytic enzymes;
the small purple granules surrounding the cells is from mast cells that have
ruptured and spilled their granules.

Mast cell tumor locations
Skin - common location
Liver
Spleen
Gastrointestinal tract
Blood stream

Signs of a mast cell tumor
The most common presentation of a mast cell tumor is a lump in the skin; about 10% of the patients will have or will develop more than one mast cell tumor.
The mass may appear as a raised pink lump (see photo below).
Sometimes the mass may be a less well defined mass.
If the lump is massaged or rubbed it may swell or form hives..called the Darier sign; this is causes by the release of histamine from the mast cells.
The photo below shows the typical appearance of a mast cell tumor, however other tumors such as benign histiocytomas can look grossly the same.

In dogs
Three centimeters or normal looking skin surrounding the tumor must also be removed with the mass. If the mast cell tumor is grade 1, only 1 cm margins need to be included in the excision. A deep layer of tissue below the tumor must also be removed. The removed tumor is painted with India ink and a pathologist examines the microscopic border of the tissue to ensure that the entire tumor has been removed.

Prognosis -Dogs
Prognosis of mast cell tumors of the skin is directly related to the grade of the tumor as determined by the biopsy results (histopathology). If the tumor has been completely removed with surgery, then recurrence of the tumor should be low.
Grade 1 - benign behavior - excellent cure rate with surgery
Grade 2 - moderately malignant behavior - recurrence rate is about 20 % with aggressive surgery
Grade 3 - very malignant tumor - only 10% of these patients are alive at 1 year - most of these have spread of tumor.
Some pathologists subclassify grade 2 mast cells as high grade 2 or low grade 2 mast cell tumors;
High grade 2 tumors behave like grade 3 tumors and low grade 2 mast cell tumors behave like grade 1 tumors.
Mast cell tumors located in the perineal region (anus, scrotum and vulva) and lips tend to have a more malignant behavior.
Dogs that have evidence of mast cells also in the internal organs, blood stream or bone marrow have a poor prognosis.
Tumors that are ulcerated may result in a poor prognosis.
Dogs that have signs of gastrointestinal ulcers (vomiting, black stools) generally have a poor prognosis.
Tumors that are large have a poor prognosis.
Tumors that have shown recent rapid growth have a poor prognosis.
Tumors that have recurred after surgical removal have a poor prognosis.
Mast cell tumors which have not changed for a period of 2 months frequently have a good prognosis.
Dogs living greater than 30 weeks after surgery and not having any recurrence of local or distant tumor are considered cured.
Prognosis of tumors of the internal organs is poor.