The biopsy specimen demonstrated a well-demarcated area of psoriasiform hyperplasia with elongate rete ridges. There were monomorphic epithelial cells containing abundant pale cytoplasm within the epidermis. A periodic acid–Schiff stain confirmed the presence of glycogen in the cytoplasm. There were a few scattered neutrophils and some hemosiderin. The lesion was diagnosed as a pigmented clear cell acanthoma. Because the lesion was almost completely removed by the biopsy procedure, and because the area had healed well and the nodule had not recurred, no further action was taken.
A Glistening Brown Nodule—Diagnosis. Arch Dermatol. 2007;143(2):255-260. doi:10.1001/archderm.143.2.255-h