Understanding biopsy report.

Dr. Marie replied:

Hi. I'm glad to hear that Honey's mass has shrunk significantly and that the infection seems to be cleared up. Let's see if I can help explain the cytology report for you.

"Cellularity is low with a mixed inflammatory cell infiltrate admixed with a few sheets of mature sebaceous epithelial cells and a small amount of blood."

This means that there weren't a lot of cells on the slide. Usually, mast cell tumors will produce a decent number of cells for the pathologist to look at. The types of cells that the pathologist is seeing look like infammation as well as sebaceous epithelial cells which are basically skin cells and then some blood.

"Cellularity slow and may not be fully representative"

Did you mean "Cellularity is low?" "Slow" doesn't really make sense here. But low would mean that there weren't a lot of cells on the slide and as such we could be missing something. This is the case almost every time we do a fine needle aspirate. It's never as accurate as looking at the entire lump as a full biopsy.

"The sebaceous epithelial cells may be contaminants from the skin or may indicate a sebaceous epithelial proliferation (rule out sebaceous hyperplasia or a benign sebaceous adenoma or other adnexal tumor)"

Sebaceous cells are basically skin cells near glands on the skin that secrete material...kind of like sweat glands in people. There are some rare situations where when we see sebaceous cells on a slide it is not just skin cells but a more serious condition such as the three mentioned above. These are really uncommon and I really wouldn't be concerned about them at this point.

"The inflammation may be related to chronic trauma, infection, foreign body, neoplasia, etc. Correlate with clinical impression."

This is the pathologist's "cover your butt" statement. They're basically saying that they think that the lump is caused by inflammation but as there are many possible causes for inflammation, no one can say for sure what the cause is. The clinical view of the lump (i.e. the history of the dog and what the vet is seeing) can help in making this decision. The options that are given here include chronic trauma (i.e. something rubbing on this area consistently), infection, foreign body (i.e. there's a splinter or something in there), neoplasia (cancer). Any time there is a lump, cancer has to be a possibility. Given that the lump has decreased by half in a short time, I would guess that this is unlikely, but we can't rule it out completely.

It's true that mast cells can change from time to time, but I wouldn't expect a mast cell tumor to shrink so much so quickly with just antibiotics. Given that the lump is near her armpit it may be that she is just irritating it as she walks and that is why it is redder after exercise.

At this point, your vet will give you the best guidance. But, if this were my case I would likely be telling you to keep an eye on things. If the lump was still there in a few weeks or if you felt it was getting bigger then I'd likely remove it and send the lump away for a complete biopsy. I'm guessing it will be gone in another few weeks though.

Hope that helps! Dr. Marie.


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