Crystal-Storing Histiocytosis of the Stomach

Abstract Introduction/Objective Crystal-storing histiocytosis (CSH) is an infrequently seen lesion comprised of eosinophilic histiocytes filled with refractile crystalline structures that most often have been characterized as IgG kappa restricted monoclonal immunoglobulins. The etiology for the mechanism of accumulation of the immunoglobulins is incompletely elucidated but numerous mechanisms have been postulated, including overproduction, faulty secretion, and impaired breakdown. Though CSH itself is a benign lesion, it has repeatedly been noted to be a harbinger of a concurrent or developing lymphoproliferative disorder. Literature review revealed a wide age range of presentations with no gender predilection and reports of this lesion occurring most commonly in the bone, kidneys, lungs, lymph nodes, and head and neck region. The gastrointestinal tract is uncommonly involved, with the stomach being the most frequently cited location. Reports of CSH in this setting have noted simultaneous infections with Helicobacter pylori and a range of associated lymphomas. Methods/Case Report We report a lesion from the stomach of a 45 year old female endoscopically described as containing patchy atrophic and nodular mucosa that was biopsied for gastric mapping in a patient with a reported history of autoimmune atrophic gastritis but without confirmatory antibodies on serology. Immunohistochemical stains highlighted a CD68 positive, smooth muscle myosin and cytokeratin negative, population of cells with cytoplasmic kappa positivity. CSH was diagnosed in a background of chronic inactive gastritis of both the antrum and fundus without evidence of H. pylori via staining or associated extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue on biopsy. Recent imaging revealed no concerning lymphadenopathy, lytic lesions, or masses. Results (if a Case Study enter NA) NA Conclusion Increasing pathologists’ awareness of this entity and its potential to be a paraneoplastic lesion is crucial, as further work-up is needed to exclude an underlying hematolymphoid neoplastic process.