Answer: Lichen sclerosis et atrophicus

Histology: The epidermis of the foreskin demonstrates a loss of the rete pegs. There is slight vacuolization of the basal cell layer. The upper dermis has a homogenized appearance with relatively acellular collagen. Focally, the superficial papillary dermis is edematous, characterized by pallor. Deep to this acellular collagen is a band-like infiltrate of predominantly lymphocytes with scattered plasma cells.

Discussion: These features are classic for lichen sclerosis et atrophicus (LSA). On the penis, the lesion is also known as ballanitis xerotica obliterans. In males, involvement of the glans and prepuce often result in phimosis. The key features of LSA are hyperkeratosis with follicular plugging, atrophy of the epidermis with hydropic degeneration of basal cells, pronounced edema and homogenization of the collagen in the epidermis and an inflammatory infiltrate in the mid dermis. In the penis, all these findings are present with the exception of follicular plugging. LSA may resemble lichen planus. However, the homogenized dermis separating the epidermis and inflammatory infiltrate is distinctive for LSA. Furthermore, in lichen planus one sees flattened squamatization of the basal cells that is not seen in LSA. Older lesions of LSA with only a slight inflammatory infiltrate may resemble scleroderma. However, in scleroderma there is a lack of hydropic degeneration of the basal cells, a lack of edema in the upper dermis, and the dense inflammatory infiltrate seen in the current case would not be present. In scleroderma, there may be a moderately intense inflammatory infiltrate between collagen bundles and around blood vessels. However, the inflammation does not have a band-like infiltrate as seen in LSA. Often in scleroderma the more pronounced inflammatory infiltrate is seen in the subcutaneous fat, which is normal is LSA.