Macroscopic and histologic characteristics of a skin lesion in the lymphomatous macaque. (A) and (B) show the macroscopic appearance of the lesions present in pigtailed macaque J94356. Note the extensive areas of involvement. The lesions are hyperkeratotic, with alopecia, and with excoriated areas surrounded by prominent borders. (C) shows a low-power magnification of the histology of a skin lesion stained with Hematoxylin and Eosin (HE). Note the profuse mononuclear cell infiltration of the dermis, dermal-epidermal junction, epidermis, periadnexal tissue, and perivascular areas. (D) shows a high-magnification view (400×) of the infiltrating cells stained with HE. Numerous mitotic figures are present on a homogeneous background. The cells have moderately sized nuclei with 1 or 2 nucleoli.