Abstract:

A 1-year-old boy developed multiple skin-colored nodules on the forehead and extremities when he was 4 months old. Physical examination revealed that his general condition was well with no hepatomegaly, splenomegaly, lymphadenectasis, testicle abnormality or gingival hypertrophy. Pathologically, the epidermis was normal, while the dermis and subcutaneous tissue were diffusely infiltrated with medium- to large-sized deformed cells, which had a small amount of cytoplasm, oval nucleus, irregular shape and fine chromatin. Some infiltrating cells had nuclear groove and nucleoli. Immunohistochemical studies showed that the tumor cells were positive for S-100 protein, CD56, CD123, CD163, CD68, Ki-67 （40%）, weakly positive for CD4 （some）, but negative for myeloperoxidase, CD1, CD21. Bone marrow smears showed a 24.5% infltration by monoblasts and promonocytes. A diagnosis of monoblastic sarcoma cutis preceding acute monoblastic leukemia was made.