Flow cytometry allows the pathologist to detect cells with abnormal proliferative behavior and DNA content. This example shows analysis of an esophageal biopsy from a patient with Barrett's esophagus. The top figure shows proliferative activity (cells stained positively with antibody to Ki-67, y-axis) vs DNA content (x-axis). There is a population of cells with high Ki-67 staining and an abnormal, increased DNA content (aneuploidy). Although there is no tumor present, the presence of this abnormal cell population indicates increased risk for the future development of cancer (American Journal of Gastroenterology, 95: 1669-1676, 2000).

This figure shows cell cycle analysis of the above data, quantitating the high S phase (20.8%) of these aneuploid cells.

Peter S. Rabinovitch MD, PhD, University of Washington, Seattle.

Multiparameter analysis of cell surface markers allows flow cytometry to help pathologists detect small populations of malignant cells when they might otherwise not be diagnosed. This example shows detection of a minimal population of abnormal T cells in bone marrow (0.3% of white blood cells), consistent with involvement by peripheral T cell lymphoma. The abnormal T cell population (red) is identified in a 4-color analysis by the expression of CD4, CD2 and CD5 at near normal levels with a loss of expression of CD3 and CD7. The abnormal population is admixed with normal CD4 (blue) and CD8 (green) T cell subsets and NK cells (orange).

Brent Wood MD, PhD, University of Washington, Seattle.

Multiparameter analysis of cell surface markers allows flow cytometry to help pathologists detect small populations of malignant cells when they might otherwise not be diagnosed. This example shows detection of a population of abnormal immature B cells in bone marrow (3% of white blood cells), consistent with persistent involvement by precursor B-cell lymphoblastic leukemia at day 21 following induction therapy. The abnormal B cell population (red) is identified in a 4-color analysis by the expression of CD19, CD22, CD10, and relatively increased CD45 and side scatter without expression of CD34 and CD20. The immunophenotype and light scatter pattern does not correspond to any normal stage of B cell maturation. The abnormal population is admixed with normal lymphocytes (blue), monocytes (orange) and myeloid cells (green).

Brent Wood MD, PhD, University of Washington, Seattle.