A centrocyte generally refers to a B cell

B cell

B cells are lymphocytes that play a large role in the humoral immune response . The principal functions of B cells are to make antibodies against antigens, perform the role of antigen-presenting cells and eventually develop into memory B cells after activation by antigen interaction...

 with a cleaved nucleus, as may appear in e.g. follicular lymphoma

Follicular lymphoma

Follicular lymphoma is the most common of the indolent non-Hodgkin's lymphomas, and the second most common form of non-Hodgkin's lymphomas overall. It is defined as a lymphoma of follicle center B-cells , which has at least a partially follicular pattern...

.

It can also refer to a cell with a protoplasm that contains single and double granules of varying size stainable with hematoxylin, as seen in lesions of lichen planus

Lichen planus

Lichen planus is a chronic mucocutaneous disease that affects the skin, tongue, and oral mucosa. The disease presents itself in the form of papules, lesions, or rashes. Lichen planus does not involve lichens, the fungus/algae symbionts that often grow on tree trunks; the name refers to the dry and...

, or a nondividing, activated B cell that expresses membrane immunoglobulin.