A 33-year-old woman presents with a lesion on the dorsum of her hand. Though it manifested several years ago, it was not problematic until recently, when it became irritated and downright painful. It has not changed in size and has never been red or swollen.
The patient denies ever having similar lesions elsewhere. She also denies any other serious health problems, specifically ophthalmologic problems.
EXAMINATION
The lesion, a 5-mm ovoid tan-orange papule, is located on the dorsum of her left hand. The surface is smooth, with a very firm feel. No skin changes are noted on the surrounding skin, and there are no palpable nodes in the arm or adjacent axilla.
In light of the patient’s concern, the lesion is excised, using an elliptical incision and minimal margins. The incision is carried down into superficial adipose tissue to ensure complete removal. Bleeding is controlled and the defect closed with simple interrupted sutures.
The pathology report shows numerous densely distributed polyhedral histiocytes. Many contain a large amount of cytoplasm.
What is the diagnosis?