haematologica vol. 87(2):february 2002 Acute Leukemias Acute erythroid neoplastic proliferations. A biological study based on 62 patients ALICIA DOMINGO-CLAROS,* ITZIAR LARRIBA,* MARUJA ROZMAN,° DOLORS IRRIGUIBLE, # TERESA VALLESPÍ, # ANNA AVENTIN, @ RAMON AYATS, @ FUENSANTA MILLÁ,^ FRANCESC SOLÉ, § LOURDES FLORENSA, § MIQUEL GALLART,** ESPERANZA TUSET,°° CARMEN LOPEZ, # SOLEDAD WOESSNER § *Ciudad Sanitaria y Universitaria de Bellvitge; °Hospital Clínic; # Hospital Valle de Hebró; @ Hospital de Sant Pau; ^Hospital Germans Trias i Pujol; § Hospital del Mar; **Hospital Arnau de Vilonova; °°Hospital de Manresa, for the Catalonian Club of Cytology, Barcelona, Spain research paper haematologica 2002; 87:148-153 http://www.haematologica.it/2002_02/148.htm Correspondence: Dr. Alicia Domingo-Claros, MD, Ciudad Sanitaria y Universitaria de Bellvitge, Feixa Llarga s/n, L’Hospitalet del Llobregat 08907, Barcelona, Spain. Phone: international +34.9.32607553. Fax: international +34.9.32607552. E-mail: alicia@domingo.com Background and Objectives. The terms acute ery- throleukemia and AML-M6 are defined in the FAB classification as proliferations of dysplastic erythroid elements mixed with blasts of myeloid origin, but pure erythroid leukemias are not included. The recent WHO classification has a category of acute myeloid leukemia not otherwise categorized, which includes acute erythroid leukemia (M6) of two sub- types: M6a-erythroleukemia (erythroid/myeloid) and M6b-pure erythroid leukemia. The aims of this co-operative study were to discover the incidences of these different subtypes, and pay special atten- tion to the morphology of these entities. Design and Methods. We reviewed a series of 62 patients with erythroid neoplastic proliferations. Pre- vious medical history, age, sex, peripheral blood and bone marrow cell counts, cytochemical stains, immunophenotype, and cytogenetics were evaluat- ed at presentation. We analyzed the incidence of erythrocyte, leukocyte and platelet abnormalities in the peripheral blood. In bone marrow we analyzed dysplastic features of erythroblasts, granulocytic elements and the megakaryocytic lineage. Results. Fifty-three patients met the criteria of M6a subtype of the WHO classification, and 2 were clas- sified as having pure erythremia (M6b); 7 cases could not be classified according to the WHO crite- ria. Fifty-five patients presented with de novo acute leukemia, and seven patients had secondary acute leukemia. The most frequent dysplastic features in blood smears were: schistocytes, tear-drop and pin- cered cells in erythrocytes; hypogranulation and hyposegmentation in leukocytes; gigantism and hypogranulation in platelets. In bone marrow, mega- loblastic changes, multinuclearity, karyorrhexis and E rythroid leukemia is a very infrequent type of acute leukemia (2-5%). Most authors agree that two main subtypes exist: the M6 acute leukemia according to the FAB criteria in which mixed granulocytic and erythroblastic cellular basophilic stippling in erythroblasts; hypogranula- tion and gigantism in granulocytic series, and micromegakaryocytes and unconnected nuclei in megakarocytes were the most dysplastic features. A positive PAS reaction and increase of bone marrow iron with ring sideroblasts were common features. Trilineage dysplasia was present in 54% of cases. Dysplastic features in granulocytic elements were absent in 26% of patients and minimal erythrob- lastic dysplasia was observed in seven patients. A complex karyotype was seen in 27% of patients; chromosomes 5 and 7 were the most frequently involved. Interpretation and Conclusions. De novo acute ery- throid leukemia was more frequent than secondary cases in our series. The most frequent type of acute erythroid proliferation was the WHO M6a subtype and the least the pure erythroid leukemia. We found a group of seven patients (11%) who could not be classified according to the WHO criteria. Morpho- logic findings of erythrocytes in peripheral blood, such as schistocytes, tear-drop and pincered cells, were outstanding features. Morphologic aspects remain one of the most important tools for diag- nosing these entities. ©2002, Ferrata Storti Foundation Key words: erythroleukemia, pure erythroid leukemia, classification, peripheral blood and bone marrow mor- phology, pincered red cells.