A Sessile histiocytoma on an ear Histiocytoma

The red lump on this dog's pinna is not a jellybean or even an engorged tick - it's a histiocytoma with a sessile attachment.

Sessile means "having a broad base".

This tumor is attached to the ear by a broad base - so we can say it is sessile. Compare this image to pedunculated, in which the mass is attached by a stem or peduncle.

So the point here is that it is important not only to describe the tumor itself (in this case: red, ovoid, smooth) but also to describe its attachment to the tissue (in this case: sessile).

Click on the image to see a 38K enlargement.

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