Langerhans Cell Histiocytosis in Bone Marrow



Langerhans Cell Histiocytosis in Bone Marrow







Key Facts


Clinical Issues



  • 2 major groups


  • Single-system Langerhans cell histiocytosis



    • Single site disease (unifocal lymph node, skin, lung, pituitary, or bone)


    • Multifocal disease (multifocal bone or multiple lymph nodes)


  • Multi-system Langerhans cell histiocytes



    • 2 or more organs involved at diagnosis without organ dysfunction


    • 2 or more organs involved at diagnosis with organ dysfunction


    • High risk: Involvement of 1 or more risk organs (liver, lung, spleen, or hematopoietic system)


    • Low risk: Involvement of other organs


Microscopic Pathology



  • Bone marrow findings



    • Patchy clusters of Langerhans cells often associated with variable numbers of eosinophils


    • Marrow involvement may be associated with fibrosis


    • Langerhans cells may also be occasionally detected on marrow aspirate smears


    • Bone marrow trephine biopsy is preferred to aspirate due to higher yield


Ancillary Tests



  • Expression of CD1a, langerin, and S100


  • Intracytoplasmic, tennis racquet-shaped Birbeck granule by electron microscopy






Wright-stained bone marrow aspirate smear from an infant with Langerhans cell histiocytosis demonstrates 2 Langerhans cells with elongated dendritic projections.






Hematoxylin and eosin-stained section of a solitary lytic lesion of the skull demonstrates a proliferation of Langerhans cells image with grooved nuclei intermixed with many eosinophils.


TERMINOLOGY


Abbreviations



  • Langerhans cell histiocytosis (LCH)


Synonyms



  • Histiocytosis X, eosinophilic granuloma (solitary lesion)


  • Hand-Schüller-Christian disease (multiple lesions)


  • Letterer-Siwe disease (disseminated disease or visceral involvement)


Definitions



  • Nonneoplastic Langerhans cells (LC)



    • First described by Paul Langerhans in 1868


    • Bone marrow-derived antigen-presenting cells


    • Normally reside in mucosal sites and epidermis


    • Migrate to lymph node following antigenic stimulation


  • Langerhans cell histiocytosis



    • Clonal proliferation of LCs in all forms except smoking-related pulmonary LCH


    • Morphologic, immunophenotypic, and ultra-structural features are similar to nonneoplastic LCs


ETIOLOGY/PATHOGENESIS


Etiology Remains Poorly Understood



  • Documented affected relative in 1% of patients


  • Higher rate of concordance for LCH in monozygotic (92%) vs. dizygotic (10%) twins


  • Reported chromosomal instability and loss of heterozygosity on chromosomes 1, 4, 6, 7, 9, 16, 17, and 22


  • No apparent genomic aberrations in some studies


CLINICAL ISSUES


Epidemiology



  • Incidence



    • 8-9 cases per 1,000,000 in children


    • 1-2 cases per 1,000,000 in adults


  • Gender



    • More common in males (M:F ratio 3.7:1)


Site



  • 2 major groups (per Histiocyte Society)


  • Single-system Langerhans cell histiocytosis



    • Single site disease (unifocal lymph node, skin, lung, pituitary, or bone)


    • Multifocal disease (multifocal bone or multiple lymph nodes)


  • Multi-system Langerhans cell histiocytosis



    • 2 or more organs involved at diagnosis without organ dysfunction


    • 2 or more organs involved at diagnosis with organ dysfunction



      • High risk: Involvement of 1 or more risk organs (liver, lung, spleen, or hematopoietic system)


      • Low risk: Involvement of other organs


Presentation

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Jun 13, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Langerhans Cell Histiocytosis in Bone Marrow

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