Follicular and mantle cell lymphoma characteristics present simultaneously in the same lymph node.

Follicular lymphoma is composed of clonal germinal center B cells. It shows a follicular pattern lacking mantle zones, with a network of interfollicular dendritic cells. Transformation to more aggressive lymphomas is documented, but the only connections to mantle cell lymphoma are described cases of composite lymphoma consisting of these 2 entities. We discuss here a case of a lymph node harboring CD20, CD10, BCL2, BCL6, cyclin D1, CD5, Ki67, and SOX11 with CD21, showing an almost intact network of dendritic cells in one part of a lymph node, and CD20, CD5, SOX11, BCL6, cyclin D1, CD10, Ki67, and CD21 cells restricted to the mantle area in another part of the same lymph node. Both parts of the lymph node had BCL2 rearrangement, a lack of t(11:14)(q13;q32), the presence of SOX11 expression, and the same clonal band. The described case suggests heterogenous development of small cell lymphomas and indicates the possibility of differentiation regression.