Follicular lymphoma

Overview
Follicular lymphoma (FL) is the most common of the indolent non-Hodgkin's lymphomas. It is defined as a lymphoma of follicle center B-cells (centrocytes and centroblasts), which has at least a partially follicular pattern. It is positive for CD10.

Morphology
The tumor is composed of follicle center cells, usually a mixture of centrocytes (cleaved follicle center cells, "small cells") and centroblasts (large noncleaved follicle center cells, "large cells"). Centrocytes typically predominate; centroblasts are usually in the minority, but by definition are always present. Rare lymphomas with a follicular growth pattern consist almost entirely of centroblasts. Occasional cases may show plasmacytoid differentiation of foci of marginal zone or monocytoid B-cells.

Causes
A translocation between chromosome 14 and 18 results in the overexpression of the bcl2 gene. This overexpression causes a blockage of apoptosis, or programmed cell death. This translocation has been associated with the development of Follicular lymphoma.

Treatment
There is no consensus regarding the best treatment algorithm, but watch-and-wait policies, alkylators, anthracycline-containing regimens (eg. CHOP), rituximab, autologous and allogeneic hematopoietic stem cell transplantation have all been applied. The disease is regarded as incurable (although allogeneic stem cell transplanation may be curative, the mortality from the procedure is too high to be a first line option). The exception is localised disease, which can be cured by local irradiation. The typical pattern is one of good responses from treatment, followed by relapses some years later. Median survival is around 10 years, but the range is wide, from less than one year, to more than 20 years. Some patients may never need treatment.