Subacute Dermal Monocytic Sarcoma: Report of a case of monocytic leukemia with initial dermal presentation only

Introduction: Monocytic sarcoma is a neoplasm of immature monocytes involving anyextramedullary site such as skin. The definite diagnosis is important for adequate therapy,which is often delayed because of misdiagnosis.Case presentation: We report a case of a 51-year-old diabetic woman who presented withsome erythematous itchy papules and plaques in scalp , trunk and upper extremities duringfive months. Clinical differential diagnosis were scleroderma of diabetes, scleromyxoma,mucinosis, eruptive histiocytosis, lepra and sarcoidosis. Microscopic evaluation of the skinbiopsy showed features of monocytic sarcoma. Pathologic differential diagnosis of theprevious skin biopsy in two months later was Dermatofibrosarcoma Protuberans andHistiocytosis.Conclusion: We present this case to alert dermatopathologists of erythematous skin lesionsclinically resembling bland-looking dermatoses such as scleroderma of diabetes,scleromyxoma, mucinosis and eruptive histiocytosis, which, in rare instances, may be apresenting feature of a monoblastic leukemia with initial dermal presentation. This entity(monoblastic leukemia cutis) poses problems for dermatopathologists even onimmunohistochemistry as monoblasts are negative for hemopoietic precursor cell antigenslike CD34, Terminal deoxynucleotidy1 transferase (TdT) and CD117. The CD34 is expressedby the blasts of most several forms of leukemia, but not by the cells of most malignantlymphomas. CD68, normally expressed by macrophages, is found on the cells of myeloid andmyelomonocytic leukemias. An important caveat is that myeloblasts react with a variety ofreagents that also identify lymphoid cells, including CD43, CD45RO, and CD20.