title: Negative images of crystalline immunoglobulin in crystal storing histiocytosis: A potential cytologic mimic of mycobacteria in smears.
abstract: Two cases are described of crystal storing histiocytosis (CSH) associated with extranodal marginal zone lymphoma, presenting as lung and subcutaneous masses respectively. Fine-needle aspiration of subcutis and smears prepared from the resected lung masses showed negative images. Cytology slides of both cases were reviewed to identify cytomorphological features for the differential diagnosis between immunoglobulin crystals and mycobacteria. The crystals in CSH consist of straight and needle shaped rods with pointed or angular edges and are more variable in thickness than the uniformly thin mycobacteria. Mycobacteria show a haphazard distribution, whereas crystals are frequently present in parallel arrays. Small lymphoid or plasma cells are identified in the background of CSH, whereas a necrotic and inflammatory background is seen in mycobacteriosis. Additional samples for culture in the case of mycobacteriosis, or flow cytometry and molecular clonality testing in the case of CSH can provide critical data for a definitive diagnosis.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada.
authors.forename: Hyang Mi
authors.initials: HM
authors.lastname: Ko
authors.forename: Gilda
authors.initials: G
authors.lastname: da Cunha Santos
authors.forename: Scott L
authors.initials: SL
authors.lastname: Boerner
authors.forename: Denis J
authors.initials: DJ
authors.lastname: Bailey
authors.forename: William R
authors.initials: WR
authors.lastname: Geddie
mesh_terms: D003460:Crystallization; D003937:Diagnosis, Differential; D005260:Female; D005542:Forearm; D006644:Histiocytes / Q000737:chemistry / Q000473:pathology*; D015620:Histiocytic Disorders, Malignant / Q000473:pathology*; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis* / Q000737:chemistry; D008168:Lung / Q000473:pathology; D018442:Lymphoma, B-Cell, Marginal Zone / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009161:Mycobacterium / Q000302:isolation & purification; D009164:Mycobacterium Infections / Q000175:diagnosis / Q000473:pathology; D010950:Plasma Cells / Q000737:chemistry / Q000473:pathology; D012983:Soft Tissue Neoplasms / Q000473:pathology
chemical_list: D007136:Immunoglobulins