Abstract
Crystal storing histiocytosis (CSH) is a very rare immunoglobulin (Ig) deposition disorder in which macrophages accumulate light chains or Ig crystalline inclusions. It is frequently associated with lymphoproliferative disorders, but can be seen in some reactive conditions too. This article reports the cytomorphologic, histopathologic, and ancillary study findings of a marginal zone B cell lymphoma of the breast with CSH in a 54-year-old woman. To the best of our knowledge, this is the first report describing CSH in the breast and one of a few reports describing the cytomorphology of CSH. In breast fine-needle aspiration biopsies, CSH can be confused with benign processes such as fat necrosis and histiocytic lesions. Thus, awareness of this rare entity and its frequent association with lymphoproliferative disorders is useful in order to triage a specimen appropriately and exclude the possibility of a lymphoproliferative process.