Mast cells

Definition:
Mast cells, so-called tissue basophils, are not a component of granulopoiesis, but rather belong to the bone marrow stroma. They are usually found in the bone marrow spicules. They are distinct from the basophils of bone marrow.

Appearance:

The basophilic granules are densely packed, thereby causing the cell to appear as a dark violet dot in low magnification. The round nucleus is only partially covered by the granules and is seen as a halo in the center.