Cutaneous granulocytic sarcoma mimicking immunoblastic large cell lymphoma

A peculiar case of cutaneous granulocytic sarcoma without leukemic manifestation (so-called aleukemic leukemia cutis) that developed in the skin of the back of a 69-year-old man is reported. A skin biopsy specimen showed atypical cells with a prominent nucleolus proliferating around dermal blood vessels and along adnexa without epidermotropism. Atypical cells similar to those of the skin had infiltrated diffusely into the interfollicular area of an inguinal lymph node. Flow cytometric and immunohistochemical studies with a panel of monoclonal antibodies revealed neoplastic cells that had a biphasic phenotype of myeloid and T cell precursors. They expressed CD13, CD15, CD33, lysozyme, CD3epsilon, CD4, CD7 and terminal deoxynucleotidyl transferase (TdT). Gene analysis showed no rearrangement of the immunoglobulin heavy chain or T cell receptor beta and gamma genes. Ultrastructurally, the tumor cells exhibited a few intracytoplasmic electron-dense granules and well-developed rough endoplasmic reticulum with an occasional whorling arrangement. The initial diagnosis was immunoblastic large cell lymphoma, and the patient was treated with six courses of ProMACE-CytaBOM. In spite of the high-grade cytological characteristics of this tumor, the patient has been free of disease for 5 years.