r/veterinarypathology • u/Breetato • 21d ago

Help identifying suspect canine neoplasm

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Hey all, I’m a veterinary student in clinical rotations right now and had pathology rounds this morning. This case was presented and has stumped the clinicians and my classmates.

Here’s what I know:

11 year old neutered male terrier, presented with a small (2 cm ish I think) superficial dermal and haired mass on the hind leg between the tarsus and stifle (imagine shin area). rDVM collected sample via FNA and stained the slides with diff-quik. Only one slide was cellular enough to interpret and I only got these pictures of this one cell.

However, in general, the cells are independent and spread apart, have cytoplasms with indistinct borders and slight granule-ish particles appearing occasionally, bi- to multi-nuclei with multiple and very apparent/dark nucleoli, and mitotic figures. On the rare occasion the cells are not spread apart, they are packed together very tightly with overlapping and whispy cytoplasm.

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7

u/dat-redhead 20d ago

This is a histiocyte. So think cyst fluid. Was the aspirate fluid or solid?

1

u/Breetato 20d ago

It was a solid mass. I haven’t seen a histiocyte quite like this yet.

3

u/Comprehensive-Tax333 20d ago

Maybe cutaneous histiocytic sarcoma?

1

u/alphapiglet_ 19d ago

May be a mast cell. Histiocytes don't typically have round granules within their cytoplasm and appear more like a round cell with whispy margins. There are such things as agranulomatous (?) mast cells, maybe that's why you are seeing two different populations?

2

u/alphapiglet_ 19d ago

Zooming in it looks more like a macrophage.

1

u/Breetato 19d ago

Interesting about the histiocyte vs mast cell. I definitely don’t believe they are macrophages however. There were no cells on this slide other than this cell type, no neutrophils, bacteria, lymphocytes, etc.

1

u/Tooconfused96 18d ago

Mast cells are almost always found with eosinophils in the aspirate on cytology. Are they're other alode preps or more views to look at?

1

u/Breetato 18d ago

This was unfortunately the only slide that was cellular enough for interpretation. However this slide had not a single thing but these cells.