I Said Something Smart Yesterday

Most days of the week we start class at 10 AM (I love the 4th semester schedule!). On Mondays we sometimes have Pathology II lab. We might be in the necropsy (animal autopsy) lab looking at preserved tissues, or in the classroom getting an extra lecture, or sometimes we don’t have lab at all. Here at the end of the semester, we’re listening to group presentations. We’re assigned to groups and given a pathologist’s report about a biopsy. We’re supposed to present this material as though we were the pathologist. We make a recommendation to the referring vet who sent in the biopsy:  further tests recommended, treatment options, prognosis, etc. We’re provided with additional relevant articles about the condition diagnosed by the biopsy. Most of the cases in the presentations are about neoplasia (abnormal growth of cells). The lumps or bumps are sent to the pathologist to find out whether they’re malignant, benign, or non-neoplastic.

Yesterday a group was presenting about plasmacytoma. Plasma cells are a type of white blood cell that secrete antibodies. They’re an important part of the body’s immune system. When one plasma cell starts replicating too quickly, you get a whole bunch of nearly identical cells. When this happens in the bone marrow, it’s very bad (it’s called multiple myeloma). When it happens in other locations, like the skin, it’s not so bad, and the lump is called a plasmacytoma.. Cutaneous (skin) plasmacytomas in animals tend to be benign (not bad).  The group presenting yesterday had a dog with a cutaneous plasmacytoma. They recommended further (expensive) tests to definitively diagnose it as a plasma cell tumor, versus other types of “round cell” tumors (a class of tumors that, well, are made up of round cells!).

After the presentation, some classmates asked some questions, then the professors had their turn to ask questions. One of them asked why bother with the expensive tests: “Do you need immunohistochemistry to confirm that this is a plasma cell tumor?” No one in the group answered, and before I knew what was happening, “NO,” came out of my mouth! This particular classroom is long, skinny, and filled with microscopes. The professor stood up to try to see between the microscopes. “Who said that?” She’d taught us to raise our hand with pride when answering, so I raised my hand, hopefully with what appeared to be pride and not fear. “I did,” I said. The professor continued, “OK, Becky. Why do you think immunohistochemistry is not necessary?” Early on (1st semester) we took a  microanatomy class to learn what different cells look like. We’d looked at plasma cells then (a year ago), and we looked at them again a couple of months ago in clinical pathology when we studied round cell tumors. Thankfully plasma cells were in my recent memory banks. “I feel that plasma cells have a distinctive morphology. They have a clear Golgi area and a wagon-wheel pattern in the nucleus. I think plasma cells can be identified in tissue by appearance, without using immunohistochemistry,” I replied. The classroom was very quiet. The other professor asked me, “Are all plasmacytomas easy to see on microscopy?” Was this a trick? “Maybe?” I guessed. “Yes,” the professor said, “Nearly all plasmacytomas are easy to identify. 9.5 times out of 10, you won’t do further testing. Nice answer.” Wheh!

The most impressive part was that I’d woken up too late to eat breakfast, forgot to grab a granola bar to eat in the car, and food isn’t allowed in the microscope lab.

Here’s a microscopic view of a plasma cell (at 100x magnification):

The one above doesn’t show the “wagon-wheel” pattern so well. If you looked really, really closely (electron microscope), this is what you’d see:

A plasma cell can be further described as having an oval shape with an eccentric (off to one side) nucleus and basophilic (blue) cytoplasm. The wagon wheel pattern in the nucleus comes from clumping of chromatin (bits of genetic material).

My group will be presenting next week, and we were assigned malignant histiocytosis. I’ll write more about this as soon as I learn more about the condition!