Melanin often stains dark blue-green (blackish) on most cyto preps and is granular within in cells but can also look like fine little rods (more brownish) when individualised, say in pigmented epithelia such as squamous cells.
Most of the cells about have a regular nucleus (small, ovoid and homogenous chromatin). These display little variation in cell size.
Melanomas are quite often infiltrated by melanophages (macrophages with engulfed melanin) - the cells above are probably melanophages.
Most melanomas in dogs in the skin are benign unlike the cat.
Quite often melanin containing cells are spindle shaped but sometimes melanin can be present in epithelia such as basal cells and thus can be difficult to distinguish cytologically.
First principals are then needed such as cell morphology, cell borders and cohesiveness.
First published: Wed, Jan 12 2011