Clonal nevus

    Article Contributors: 
    Sean Klepper M.D.
    Artur Zembowicz M.D....

    Also known as: inverted type A nevus

    Clinical Features:

    • This refers to discrete nests of nevus cells within the dermal component of an ordinary nevus.
    • Often not recognized clinically, unless a change--such as a change in color--occurs in a common or congenital nevus

    Histologic Features:

    • Typically well-circumscribed nests of nevus cells within the upper dermis of a common or less often congenital nevus
    • The clonal nests stand out as being morphologically quite different from the background nevus cells: the clonal cells are usually epithelioid, with abundant pigmented cytoplasm and irregular nuclei with small nucleoli.  In contrast, the background nevus cells are typically of the type B ("lymphocyte like") variety.
    • Melanophages are usually abundant in the adjacent dermis.
    • Mitoses are absent or very rare.