...Don't think much.' Ted Williams
'True. But that's precisely when you should be doing your research!' YBD
I feel quite confident now that I have a firm understanding of Mast Cell Tumors (MCT) and I wanted to share some of that with you.
First off, I searched extensively for the most thorough though lucid account of this type of cancer from a microbiological and immunological perspective. And that follows:
A normal mast cell is part of our immunologic defense systems against invading organisms. Mast cells are meant to participate in the war against parasites (as opposed to the war against bacterial or viral invaders). They are bound within tissues that interface with the external world such as the skin, respiratory or intestinal tract. They do not circulate through the body.
The mast cell possesses within itself granules of especially inflammatory biochemicals meant for use against invading parasites. (Think of these as small bombs that can be released). The mast cell has binding sites on its surface for a special type of antibody called IgE. IgE is produced in response to exposure to antigens typical of parasites (i.e., worm skin proteins, or similarly shaped proteins). IgE antibodies, which are shaped like tiny "Y"'s, find their way to a tissue mast cell and perch there. With enough exposure to the antigen in question, the mast cell may be covered with Y- shaped IgE antibodies like the fluff of a dandelion. The mast cell is said, at this point, to be sensitized.
As said, the IgE antibodies are Y-shaped. Their foot is planted in the mast cell while their arms lift up hoping to capture the antigen for which they were individually designed. When the antigen comes by and is grasped by the IgE antibodies, this should indicate that a parasite is near and the mast cell, like a land mine, degranulates releasing its toxic biochemical weapons. These chemicals are harmful to the parasite plus serve as signals to other immune cells that a battle is in progress and for them to come and join in.
At least this is what is supposed to happen.
A mast cell, coated with IgE antibodies, is exposed to pollen and degranulates, releasing its biochemical weapons of destruction.
The problem is that we live in a clean world without a lot of parasites. What unfortunately tends to happen is that the IgE/mast cell system is stimulated with other antigens that are of similar shape or size as parasitic antigens. These "next best" antigens are usually pollen proteins and the result is an allergy. Instead of killing an invading parasite, the mast cell biochemicals produce local redness, itch, swelling, and other symptoms we associate with allergic reactions.
As if the mast cell isn't enough of a troublemaker in this regard, the mast cell can form a tumor made of many mast cells. When this happens, the cells of the tumor are unstable. This means they release their toxic granules with simple contact or even at random creating allergic symptoms that do not correlate with exposure to any particular antigen.
There's additional info on diagnosis, grading, treatment etc. here.
To Chemo or Not to Chemo
Now that we have received the initial pathology report as a Grade II with a low mitotic index, some of the oncologists with which I consulted have recommended a 'Wait and See' approach with quarterly re-checks since we had wide surgical margins.
However, since some Grade II tumors don't always behave predictably, others suggested two additional tests. The first is the mast cell tumor panel that consists of two proliferation markers - PCNA and Ki67. It has been demonstrated that dogs that have more rapid rate of cell proliferation are more likely to have an aggressive form of MCT and chemotherapy might be warranted.
The second is know as the c-kit mutation. It's been shown that about half of grade II MCTs have mutations in the proto-oncogene, c-kit, and were more likely to recur after surgery and metastasize.
Mac and Me
Hudson's tumor, affectionately known now as Mac, has been sent out and we're awaiting the results of both tests. By Monday, hopefully, as that effects the decision I make about his treatment plan. For now, more waiting. And waiting. But having completed my research, I guess I can go back to not thinking much.
I've compiled in excess of over fifty pages of research, links, etc. that I'd be happy to share upon request. Email me at firstname.lastname@example.org Some of the information is repetitious but for me, that's just a way I make certain I retain it.