From the archives of MD Anderson Cancer Center: Crystal-storing histiocytosis associated with B-cell lymphoma.

Crystal-storing histiocytosis (CSH) is rare morphologic manifestation of disease histologically characterized by benign histiocytes, usually numerous, filled with cytoplasmic eosinophilic crystals. More than 200 cases have been reported in the literature. In most CSH cases, affected patients also have a plasma cell neoplasm or B-cell lymphoma. We report a 61-year-old man with a remote history of resected colon adenocarcinoma. As part of surveillance imaging he was found to have a 5.5 cm right ureteral/periureteral mass causing hydronephrosis, multi-station lymphadenopathy and splenomegaly. CT-guided biopsy obtained from the mass showed that ≥95% was composed of sheets of histiocytes containing abundant cytoplasmic crystals. The remainder of the specimen was composed of small lymphocytes and plasma cells. Immunohistochemical analysis showed that the lymphocytes were mostly positive for CD5, CD20 and PAX5, and negative for CD3. The plasma cells were positive for monotypic cytoplasmic kappa, CD138 and MUM1/IRF4, and the histiocytes were positive for CD31, CD68, and CD163, with crystals positive for CD68 and MUM1/IRF4. Subsequent bone marrow evaluation with flow cytometry immunophenotypic analysis showed a small monotypic kappa-positive B-cell population positive for CD5, CD19, CD20 and CD23. These findings support the diagnosis of CSH with immunoglobulin crystals associated with B-cell lymphoma. We review the literature on CSH associated with immunoglobulin crystals and discuss the differential diagnosis.