Hematoxylin-eosin–stained biopsy specimens revealed a sharply demarcated, acanthotic epidermis composed of enlarged keratinocytes that had strikingly lighter-stained cytoplasm than those in the adjacent, uninvolved epidermis. Spongiosis and minimal exocytosis of neutrophils were evident. The rete ridges were elongated. Overlying the epidermis were parakeratosis and a thinned-to-absent granular layer. The superficial dermis, as well as the dermal papillae, contained increased numbers of prominent capillaries. There was a moderate superficial perivascular lymphocytic infiltrate (Figure 2).
Multiple Asymptomatic Papules in the Popliteal Fossa. Arch Dermatol. 1998;134(6):743-748. doi: