Cytology of a mast cell tumor from a Labrador Retriever. The magnification is 1000x.  The cells are mast cells (although there are two granulocytes at the bottom and possibly a fibroblast to the right). The purple granules that are present in the cells are granules that contain histamine.  Slide was stained with a modified Wright's stain.
<a href="//commons.wikimedia.org/wiki/User:Joelmills" title="User:Joelmills">Joel Mills</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>