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June 2009

A Violaceous Nodule on the Knee—Quiz Case

Author Affiliations

Copyright 2009 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.2009

Arch Dermatol. 2009;145(6):715-720. doi:10.1001/archdermatol.2009.111-a

A 69-year-old white woman presented with an 8-month history of a reddish nodule on her right knee. She had initially noted the lesion after she bumped her knee on a cabinet drawer. The nodule had begun as a small pimplelike lesion and had progressively and slowly grown over the next several months. The patient, who was in otherwise good health, denied any other symptoms. She had no history of skin cancers or atypical moles and no family history of melanoma.

Physical examination revealed a 2-cm, violaceous, conical-shaped nodule, which was firm, nontender, and freely mobile, with a smooth surface and a small central crust (Figure 1). There was no lymphadenopathy. A punch biopsy specimen was obtained for histopathologic examination (Figure 2 and Figure 3).