Abstract
BACKGROUND: Crystal-storing histiocytosis (CSH) is a rare disorder which most commonly occurs in the setting of concurrent lymphoproliferative disease. Morphologically, it consists of aggregates of histiocytes containing eosinophilic crystalline material, which in most cases is composed of aggregated abnormal light chains. METHODS: Using histomorphology, immunohistochemistry and in situ hybridization, the authors characterize a rare case of orbital CSH associated with extranodal marginal zone (MALT) lymphoma and report for the first time the frozen section features of CSH. RESULTS: The frozen section featured plump histiocytes with ample weakly basophilic to grayish cytoplasm with a microvacuolated appearance and focal stippling. These features stand in contrast with the formalin-fixed, paraffin embedded histomorphological appearance of aggregates of plump histiocytes with densely eosinophilic crystalline cytoplasmic material. CONCLUSION: CSH is a challenging diagnosis to make on frozen section. The artifacts that preclude its recognition, as well as differential diagnoses of this entity in the head and neck are discussed.