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* Context.--In comparison to [alpha][beta] T cells, little is known about the immunophenotype of healthy peripheral blood [gamma][delta] T cells or about conditions associated with expansion of this usually minor T-cell subset. Objective.--To study the immunophenotype of increased nonneoplastic peripheral blood [gamma][delta] T cells and to determine clinical conditions associated with this laboratory finding. Design.--Flow cytometric T-cell phenotyping studies performed on 352 consecutive peripheral blood specimens were reviewed, and 62 cases (18%) in which [gamma][delta] T cells comprised either more than 5% of the total lymphocytes or had an absolute count of more than 200 cells per [micro]L or both, were studied further. Clinical data were available from 36 cases. Results.--The [gamma][delta] T cells often had an immunophenotype distinct from the [alpha][beta] T cells, with differences in CD5 expression as the most common (n = 17), followed by differences in CD3 (n = 6) and CD7 (n = 3). CD16 coexpression by the [gamma][delta] T cells was also frequent (n = 20). In 28 (78%) of 36 cases, there were one or more associated conditions: infection/inflammatory disease (n = 18), autoimmune disease (n = 9), lymphoproliferative disorder (n = 6), and splenectomy (n = 3). Conclusions.--Circulating [gamma][delta] T cells are immunophenotypically distinct from ap T cells, and mild increases in these cells are not uncommon and may be associated with immune system activation and splenectomy. Recognition of this phenomenon is important because reactive [gamma][delta] T cells can exhibit distinctive immunophenotypic features that are also encountered in neoplastic conditions, such as T-cell large granular lymphocytic leukemia., Early in their ontogeny, T cells commit to express either [alpha][beta] or [gamma][delta] T-cell receptor (TCR) heterodimers, resulting in phenotypically and functionally distinct T-cell lineages. (1) In healthy adults, [alpha][beta] [...]

Context.--The immunophenotypic profile of basophils is not yet fully established, and the immunophenotypic changes in chronic myelogenous leukemia are not fully characterized. Objective.--To establish a comprehensive immunophenotypic spectrum of normal basophils and to assess the range of immunophenotypic aberrations of basophils in chronic myelogenous leukemia. Design.--Using 4-color flow cytometry, we compared the immunophenotypic profile of basophils in peripheral blood or bone marrow samples from 20 patients with no evidence of neoplasia to basophils from 15 patients with chronic myelogenous leukemia. Results.--Basophils in control cases were all positive for CD9, CD13, CD22, CD25 (dim), CD33, CD36, CD38 (bright), CD45 (dimmer than lymphocytes and brighter than myeloblasts), and CD123 (bright), and were negative for CD19, CD34, CD64, CD117, and HLA-DR. Basophils in all chronic myelogenous leukemia patients possessed 1 to 5 immunophenotypic aberrancies. The most common aberrancies were underexpression of CD38, followed by aberrant expression of CD64 and underexpression of CD123. CD34 and CD117 were present in cases with basophilic precursors. Myeloblasts showed a distinct immunophenotypic profile, as they typically expressed CD34 and CD117, showed dimmer expression (compared with basophils) of CD38, CD45, and CD123, and lacked expression of CD22. Conclusions.--Flow cytometric immunophenotyping can identify immunophenotypic aberrations of basophils in chronic myelogenous leukemia, and discriminate basophils from myeloblasts., Basophils are the least common blood granulocytes, with a prevalence of about 0.5% of total leukocytes and about 0.3% of nucleated marrow cells in a healthy individual, (1,2) and acute [...]

Context.--In the diagnosis of lymphomas and leukemias, flow cytometry has been considered an essential addition to morphology and immunohistochemistry. The interpretation of immunophenotyping results by flow cytometry involves pattern recognition of different hematologic neoplasms that may have similar immunologic marker profiles. An important factor that creates difficulty in the interpretation process is the lack of consistency in marker expression for a particular neoplasm. For this reason, a definitive diagnostic pattern is usually not available for each specific neoplasm. Consequently, there is a need for decision support tools to assist pathology trainees in learning flow cytometric diagnosis of leukemia and lymphoma. Objective.--Development of a Web-enabled relational database integrated with decision-making tools for teaching flow cytometric diagnosis of hematologic neoplasms. Design.--This database has a knowledge base containing patterns of 44 markers for 37 hematologic neoplasms. We have obtained immunophenotyping data published in the scientific literature and incorporated them into a mathematical algorithm that is integrated to the database for differential diagnostic purposes. The algorithm takes into account the incidence of positive and negative expression of each marker for each disorder. Results.--Validation of this algorithm was performed using 92 clinical cases accumulated from 2 different medical centers. The database also incorporates the latest World Health Organization classification for hematologic neoplasms. Conclusions.--The algorithm developed in this database shows significant improvement in diagnostic accuracy over our previous database prototype. This Web-based database is proposed to be a useful public resource for teaching pathology trainees flow cytometric diagnosis. (Arch Pathol Lab Med. 2008;132:829-837), The use of flow cytometry in immunophenotyping has undoubtedly added an essential dimension to the diagnosis of hematologic neoplasms. (1,2) Hematologic cells express a wide range of cell surface and [...]