Papillary eccrine adenoma.

An example of papillary eccrine adenoma was seen. This benign cutaneous tumor has a diagnostic microscopic appearance that consists of multiple ducts lined by two or more layers of cells. The inner layer often forms one or multiple papillae of variable complexity. The stroma consists of patches of loosely arranged spindled cells and areas of hyalinized collagen. The latter often forms bands about the ducts. In addition to the foregoing, we observed focal squamous differentiation, clear cell change, connection of ducts to the epidermis, and prominent nerves within the stroma. Papillary eccrine adenoma also has several characteristic clinical features. The tumors are firm or hard nodules, frequently of many years' duration, and a large proportion are situated on the extremities of black persons.