Crystal-storing histiocytes in ascites leading to a diagnosis of plasma cell myeloma.

Histiocytes containing multiple needle-shaped eosinophilic crystals visualized in a peritoneal fluid sample during evaluation of a patient for liver transplantation led to the diagnosis of unsuspected IgA kappa myeloma. Crystal-storing histiocytosis is a rare phenomenon typically associated with multiple myeloma and B-cell lymphoproliferative disorders. It can involve almost any anatomic site and can occasionally be seen in body fluid samples.