Dermatofibroma (fibrous histiocytoma)

    Clinical Features:

    • Most common in young to middle-aged adults
    • Small nodule or papule
    • The overlying skin may erythematous or hyperpigmented and often shows the "dimple sign": central dimpling when the lateral borders of the lesion are compressed.
    • Benign; rarely recurs, with the exception of the cellular and aneurysmal variants
    • The aneurysmal variants may attain a large size, raising concern clinically for a malignant neoplasm.

    Histologic Features:

    • A heterogeneous tumor, with a number of variants (described below)
    • All variants show a fairly well-circumscribed dermal proliferation of spindled "fibrohistiocytic "in tight fascicles, with a storiform pattern
    • Cytologically, the cells have vesicular nuclei with scant to fairly abundant amphophilic cytoplasm.
    • The cells characteristically wrap themselves around dermal collagen bundles, which may be hyalinized.
    • Admixed lymphocytes, histiocytes, xanthoma cells and/or Touton-type giant cells may be present.
    • The overlying epidermis is usually acanthotic and often hyperpigmented, but may instead sometimes show thinning.
    • Occasionally, extension into the superficial subcutaneous fat may be present.
    • Variants:
      • Sclerosing hemangioma: a highly vascular dermatofibroma
      • Hemosiderotic histiocytoma: a dermatofibroma with extensive hemosiderin deposition
      • Aneurysmal benign histiocytoma: highly cellular variant with multiple pseudovascular spaces (devoid of an endothelial lining)
      • Dermatofibroma with monster cells (atypical benign fibrous histiocytoma): an otherwise typical dermatofibroma with scattered bizarre giant cells
      • Epithelioid benign fibrous histiocytoma: comprised of polygonal or rounded cells with abundant eosinophilic cytoplasm, frequently showing binucleation.  Often exophytic with a collarette.
      • Cellular variant: highly cellular often mimicking DFSP or leiomyosarcoma.  Often shows focal necrosis and extension into the subcutaneous fat.
      • Palisading variant: focal prominent nuclear palisading
      • Clear cell dermatofibroma: composed predominantly of clear cells
    External Links:

    Cases associated with this book:

  • Dermatofibroma
    Author: Stephen Lyle, M.D., Ph.D.

    Conference: DermatopathologyConsultations.com Teaching Collection