Monocytic sarcoma is a neoplasm of immature monocytes involving any extramedullary site such as skin. The definite diagnosis is important for adequate therapy, which is often delayed because
of misdiagnosis. We report a 51-Year-old diabetic woman who presented with several erythematous itchy papules and plaques on her scalp, trunk and upper extremities during a five-month period.
Clinical differential diagnoses were scleredema diabeticorum, scleromyxoma, mucinosis, eruptive histiocytosis, leprosy and sarcoidosis. Skin biopsy showed features of monocytic sarcoma. We
present this case to alert dermatologists and dermatopathologists of erythematous skin lesions clinically resembling bland-looking dermatoses such as scleredema diabeticorum, scleromyxoma,
mucinosis and eruptive histiocytosis, which, in rare instances, may be a presenting feature of a monoblastic leukemia with initial dermal presentation.