A Case of Leukemia Cutis (Acute Myeloid Leukemia) With Epidermotropism.

Acute myeloid leukemia is a cancer involving uncontrolled proliferation of hematopoietic cells. Cutaneous involvement is referred to as leukemia cutis (LC). The histopathologic presentation of LC is variable, and may present with perivascular, periadnexal, dermal, or subcutaneous infiltrate. Epidermotropism is notably absent. We report an unusual case of acute myeloid LC with epidermotropism in a 68-year-old man. A punch biopsy revealed a mononuclear myeloblast infiltrate involving the dermis and subcutaneous tissue. The epidermis was focally acanthotic, with several vesicles and atypical epidermotropic cells. Mitotic figures and apoptotic cells were present. Immunohistochemistry showed the blasts to be positive for CD56, CD123, and lysozyme, and weakly positive for CD4 and CD163. Negative immunostaining included CD3, CD20, CD34, TdT, and CD117. Epstein-Barr virus in situ hybridization was negative. A bone marrow biopsy revealed the same myeloblast population with identical phenotype to the skin. The blasts were negative for CD34, CD117, CD3, CD19, CD163, CD68, CD61, myeloperoxidase, pankeratin, E-cadherin, CD4, and transcription factor 4. A diagnosis of acute myeloid leukemia with monocytic differentiation and leukemia cutis was established. These findings suggest that the differential diagnosis for conditions with epidermotropism may be even broader than previously thought.