Fig. 2

Punch biopsy of the skin showing superficial epidermal involvement by a hematopoietic neoplasm. Epidermal erosion and ulceration with underlying hematopoietic infiltrate involving epidermis and upper dermis (a; H&E stain, 100× magnification). The hematopoietic neoplasm is poorly differentiated with blastic nuclear features and round to reniform nuclei. Cellular apoptosis is increased. Numerous small reactive lymphoid cells are also present (b; 500× magnification). The majority of the blastic cells express CD1a by immunohistochemistry (c; 500× magnification) and coexpress langerin (d; 500× magnification). The findings are those of acute monoblastic leukemia with Langerhans cell differentiation involving skin