Non-Langerhans Cell Histiocytoses



Non-Langerhans Cell Histiocytoses


Aaron Auerbach, MD, PhD










Indeterminate cell histiocytosis is a very rare histiocytosis composed of cells with histologic and immunohistochemical similarities to Langerhans cells, but lacking Birbeck granules by electron microscopy.






Hereditary progressive mucinous histiocytosis shows a dermal proliferation composed of epithelioid histiocytes image and mucin separating broad bundles of collagen image.


TERMINOLOGY


Synonyms



  • Non-X histiocytoses


Definitions



  • Wide range of histiocytic disorders that are not derived from Langerhans cells



    • Sometimes difficult to categorize because of overlapping morphologic and clinical findings


    • Includes juvenile xanthogranuloma, reticulohistiocytoma, and Rosai-Dorfman disease


  • Histiocyte = bone marrow-derived cell belonging to monocytes/macrophage &/or dendritic cell lineage and functional variants



    • Includes macrophages, Langerhans cells, interstitial dendritic cells, interdigitating dendritic cells, plasmacytoid dendritic cells, microglia, Kupffer cells, and alveolar macrophages


CLINICAL ISSUES


Epidemiology



  • Age



    • Depends on type of histiocytosis


Treatment



  • Benign tumors that do not require treatment in most cases


Prognosis



  • Depends on type of histiocytosis


MICROSCOPIC PATHOLOGY


Histologic Features



  • Macrophages are large (15-25 µm in diameter) phagocytic cells with irregular shapes and pseudopodia



    • Nucleus is round, but may be indented or reniform


    • Nuclear membrane is indistinct, and chromatin is fine


    • Cytoplasm is abundant and can be granulated


    • Cytoplasmic vacuoles may be seen, and phagocytosed material may be present


  • Other features depend on the type of histiocytosis


ANCILLARY TESTS


Immunohistochemistry



  • Depends on type of histiocytosis



    • Macrophages are typically positive for CD14, CD68, and CD163


    • Dermal/interstitial dendritic cells are positive for FXIIIA, CD14, CD163, and fascin


    • Indeterminate cells are S100(+), CD1a(+), FXIIIA(+)


Electron Microscopy



  • Non-Langerhans cell histiocytoses do not have Birbeck granules by ultrastructural studies, unlike Langerhans cell histiocytosis (LCH)


DIFFERENTIAL DIAGNOSIS


Benign Cephalic Histiocytosis



  • Rare histiocytosis characterized by asymptomatic, self-healing reddish to brownish macules and papules on the head, which spread later to trunk and arms



    • Begins in children ≤ 3 years old


  • Morphology



    • Dermal histiocytes, fairly small with round nuclei



      • ± vacuolated cytoplasm


      • Positive for CD68, CD11a, and CD11c; negative for S100 and CD1a


    • Patterns include papillary dermal, lichenoid, and diffuse



      • Usually no epidermotropism



  • Electron microscopy shows comma-shaped bodies, coated vesicles, and desmosome-like structures with absence of Birbeck granules


Generalized Eruptive Histiocytoma



  • Rare benign histiocytosis characterized by crops of hundreds of blue-red papules, affecting mainly adults, and self-healing



    • Symmetrically distributed on trunk and extremities



      • May become hyperpigmented macules when they regress


  • Clinical course



    • Usually self-limiting; may last from 1 month to over 12 years



      • May persist, may resolve, or may relapse


    • Sometimes associated with underlying tumors



      • Macules/papules may regress when underlying malignancy is treated


  • Morphology



    • Histiocytes in upper dermis



      • Sometimes small and vacuolated cytoplasm


      • ± perivascular distribution


    • Usually no multinucleated giant cells


    • Older lesions may show fibrosis or giant cells


    • CD68(+), S100(-), CD1a(-)


  • Electron microscopy shows dense bodies with myelin, but no Birbeck granules


Indeterminate Cell Histiocytosis (ICH)



  • Dendritic cells in dermis with features of histiocytes and Langerhans cells but no Birbeck granules



    • Only few cases reported


  • Presentation



    • Numerous red/brown papules



      • May coalesce


  • Morphology



    • Monomorphous infiltrate of mononuclear histiocytes intermixed with clusters of lymphocytes



      • Rarely multinucleated cells


      • Often increased numbers of reactive T cells interspersed among histiocytic cells


      • Usually ample pale cytoplasm and clefted nuclei


      • Rare spindle cell variant has been described


      • Stroma can be myxoid


    • Immunohistochemistry



      • S100(+), CD68(+), CD1a(+), FXIIIA(±)


  • Sometimes look like Langerhans cells with ample cytoplasm and grooves



    • But lack some Langerhans markers such as Langerin and Birbeck granules


Progressive Nodular Histiocytosis

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Non-Langerhans Cell Histiocytoses
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