Kaposi sarcoma

    Article Contributors: 
    Sean Klepper M.D.
    Stephen Lyle, M.D., ...

    Clinical Features:

    • A vascular neoplasm of intermediate malignant potential that primarily affects the skin, but which may affect multiple other organs as well.
    • Apparently caused by human herpes virus-8 (HHV-)
    • Several clinical forms exist:
      • Classic (or European):
        • Most commonly affects older men of Ashkenazi Jewish or Mediterranean origin
        • Typically begins on the distal lower extremities, followed by spread and coalescence of the lesions, with lesions of different stages often present in a single patient
        • Indolent course
      • African (endemic):
        • Common in equatorial Africa
        • Male predominance, typically affecting children and young adults
        • Heterogeneity of clinical presentation, ranging from nodular lesions pursuing an indolent course to florid involvement of the skin and/or lymph nodes, sometimes with bone involvement
      • AIDS-associated (epidemic):
        • Among patients with AIDS, by far the most common in homosexual males
        • Typically presents as a few small pink to violaceous lesions on the upper body
        • Often progress to disseminated disease
      • Immunosuppression:
        • Most common in the setting of organ transplantation
        • As is the case with the classic form of Kaposi sarcoma, there is a predisposition for individuals of Ashkenazi Jewish or Mediterranean descent, but women are more commonly affected than in the classic form.
        • May present at multiple cutaneous or visceral locations
        • Tends to progress to disseminated disease, but the lesions often regress upon reduction of immunosuppression
      • Rare variants are the Stewart-Treves-like variant which occurs many years after an ipsilateral radical mastectomy in the setting of chronic lymphemema, and the lymphangioma-like variant, which often presents clinically as a bulla.

    Histologic Features:

    • Kaposi sarcoma evolves histologically through three stages: patch, plaque and nodular.
    • Plaque stage:
      • Inconspicuous proliferation of bland, angulated, thin-walled blood vessels which tend to surround non-neoplastic dermal blood vessels and adnexae.
      • The features may be quite subtle, but a clue to the diagnosis is that the neoplastic vessels show slit-like, angulated lumina.
      • An additional helpful feature when present is the promontory sign, a term used for the finding of neoplastic vessels protruding into the lumen of a pre-existing vessel or surrounding and "isolating" a normal dermal structure.
      • In the early plaque stage, the vascular proliferation is confined to the reticular dermis, often only the superficial aspects of it; in later lesions, the entire dermis is involved.
      • A perivascular lymphocytic infiltrate, often also containing some plasma cells, is typically present.
      • Additional helpful, but not diagnostic, features that may sometimes be seen are: scattered bland spindle cells associated with the neoplastic vessels, apoptotic endothelial cells, extravasated erythrocytes, hemosiderin deposition and PAS-positive hyaline globules.
    • Patch stage:
      • At this stage, the lesion fills the entire dermis and extends into the superficial subcutis.
      • The defining feature is the presence of bland spindle cells interspersed between dermal collagen bundles.
      • Present between the spindle cells are irregular, slit-like vascular channels containing scant erythrocytes.
      • The perivascular lymphoplasmacytic infiltrate seen in the plaque stage remains present.
      • Hemosiderin deposition and hyaline globules are more prominent than in the plaque stage.
      • The periphery of the lesion shows features identical to those of the plaque stage.
    • Nodular stage:
      • Dense proliferation of mildly to moderately atypical spindle cells in intersecting fascicles
      • Interspersed among the spindle cells are slit-like vascular channels containing erythrocytes.
      • Mitotic figures may be numerous.
      • An associated lymphoplasmacytic infiltrate is present.
      • Apoptoses, hemosiderin deposition and hyaline globules are frequent.
      • Ectatic blood vessels and lymphatics are often present at the periphery of the tumor nodules.
    • Immunohistochemically, Kaposi sarcoma is positive for C31, CD34 and CD40, weakly positive for Ulex europaeus and negative to weakly positive for factor VIII-related antigen.

    Cases associated with this book:

  • Kaposi sarcoma, nodular stage
    Author: Stephen Lyle, M.D., Ph.D.

    Conference: Dermpedia Teaching Collection
  • Kaposi sarcoma, early patch stage
    Author: Sean Klepper M.D.

    Conference: Dr. Z's Consultations