Crystal-storing histiocytosis and associated marginal zone lymphoma with extensive plasmacytic differentiation.

Crystal-storing histiocytosis (CSH) is a non-neoplastic histiocytic proliferation that results from the intra-lysosomal accumulation of immunoglobulins as crystals. CSH is frequently associated with various B-cell lymphomas or plasma cell neoplasms. CSH can potentially obscure underlying lymphoproliferative neoplasms. This association should always be considered and the tissue should be carefully evaluated.