Myeloid sarcoma: clinico-pathologic, phenotypic and cytogenetic analysis of 92 adult patients.

Myeloid sarcoma (MS) is a rare neoplasm whose knowledge is largely based on case reports and/or technically dated contributions. Ninety-two MSs in adulthood with clinical data available were evaluated both morphologically and immunohistochemically. Seventy-four cases were also studied by fluorescent in situ hybridization on tissue sections and/or conventional karyotyping on bone marrow or peripheral blood. Histologically, 50% of the tumors were of the blastic type, 43.5% either monoblastic or myelomonocytic and 6.5% corresponded to different histotypes. CD68/KP1 was the most commonly expressed marker (100%), followed by myeloperoxidase (83.6%), CD117 (80.4%), CD99 (54.3%), CD68/PG-M1 (51%), CD34 (43.4%), terminal-deoxy-nucleotidyl-transferase (31.5%), CD56 (13%), CD61/linker for activation of T cells (2.2%), CD30 (2.2%) and CD4 (1.1%). Foci of plasmacytoid monocyte differentiation were observed in intestinal cases carrying inv16. Chromosomal aberrations were detected in about 54% of cases: monosomy 7(10.8%), trisomy 8(10.4%) and mixed lineage leukemia-splitting (8.5%) were the commonest abnormalities, whereas t(8;21) was rare (2.2%). The behavior was dramatic irrespective of presentation, age, sex, phenotype and cytogenetics. Most if not all, long survivors received bonemarrow transplantation. The present report expands the spectrum of our knowledge showing that MS has frequent monoblastic/myelomonocytic differentiation, displays distinctive phenotypic profile, carries chromosomal aberrations other than t(8;21), and requires supra-maximal therapy.