Immunophenotyping has become common in the diagnosis and classification of acute leukemias and is particularly important in the proper identification of cases of minimally differentiated acute myeloid leukemia (AML-MO). To evaluate the immunophenotype of adult AML, 106 cases were studied by cytochemical analysis and by flow cytometry with a panel of 22 antibodies. The results were compared with the French-American-British (FAB) Cooperative Group classification, as well as with available cytogenetic data on each case. CD45, CD33, and CD13 were the most commonly expressed antigens (97.2%, 95.3%, and 94.3%, respectively). Lymphoid-associated antigens were expressed in 48.1% of cases. CD20 was the most commonly expressed lymphoid antigen (17%), although often expressed in only a subpopulation of leukemic cells, followed by CD7 (16%), CD19 (9.8%), CD2 (7.5%), CD3 (6.7%), CD5 (4.8%), and CD10 (2.9%). Some immunophenotypes correlated with FAB type, including increased frequency of CD2 expression in AML-M3; lack of CD4, CDllc, CD36, CD117, and HLA-DR expression in AML-M3; increased frequency of CD20 and CD36 expression and lack of CD34 expression in AML-M5; increased frequency of CD5 expression in AML-M5a; and increased frequency of CD14 expression in AML-M5b, when compared with all other AMLs (P < .05). When compared with AML-

Immunophenotypic studies are essential to distinguish acute lymphoblastic leukemia (ALL) from minimally differentiated acute myeloid leukemia (AMLM0) and to classify ALL into immunologic subtypes. Frequently, immunophenotyping identifies myeloid antigen expression in ALL, causing a potential diagnostic problem. To evaluate the immunophenotype of ALL, we studied 210 cases of pediatric and adult ALL by flow cytometry and compared the results with the French-American-British (FAB) Cooperative Group classification and the karyotypic findings. Myeloid-associated antigens were expressed in 78 (45.6%) of precursor B-cell ALL cases. Pediatric precursor B ALLs had a higher frequency of myeloid antigen expression than did adult cases. All mature B-cell ALL cases were negative for TdT and myeloid antigens. Myeloid antigen expression was less frequent in T-cell ALL cases compared with precursor B-cell ALL cases. Of the 192 cases submitted for cytogenetic analysis, 147 were abnormal. The most common chromosomal translocation was the Philadelphia chromosome, which was more likely to have L2 blast morphology and a precursor B immunophenotype. Myeloid antigen expression was present in 70.8% of Ph-positive cases (P = .008). Chromosome rearrangements involving 11q23 also showed an increased frequency of myeloid antigen expression. Chromosome translocations involving regions of T-cell receptor genes were present in 24% of T-cell ALL cases. A high percentage of ALL cases, however, had various other cytogenetic abnormalities, many of which involved less well-studied chromosomal regions.

An association between Epstein-Barr virus and Hodgkin lymphoma has been shown in several parts of the world. The reported incidence of Epstein-Barr virus in Hodgkin lymphoma varies significantly from one country to another and ranges from <30% in Swedish patients to 100% in patients from Kenya. Using in situ hybridization for detection of Epstein-Barr virus-encoded RNA and immunohistochemistry for detection of Epstein-Barr virus latent membrane protein, we analyzed 28 cases of Hodgkin lymphoma from Jordan and 30 cases from the United States. Eight of 28 Jordanian cases and 9 of 30 North American cases were Epstein-Barr virus positive. Our studies show that the incidence of Epstein-Barr virus among Jordanian patients with Hodgkin lymphoma is similar to the rate in patients from the United States. This rate appears to be low to intermediate compared with rates in other parts of the world.

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