Haematoxylin-eosin–stained sections demonstrated a moderately dense infiltrate of lymphohistiocytic cells extending from the papillary to the midreticular dermis. Immunocytochemical staining of the lymphocytic infiltrate revealed a predominance of T cells, but some B cells were also identified. Many of the cells stained with the histiocytic markers Mac-387 and CD68. Staining was negative for S100 protein.

On electron microscopy, a population of histiocytes was identified, but no Birbeck granules (specific for Langerhans cells) were present. Dense bodies and comma-shaped bodies were identified in some of the cells.

During 4 years of follow-up, the patient has received no specific treatment and continues to develop occasional new lesions. There has been no clinical indication of disease transformation or development of systemic disease.