For chromosomal analysis in tumor genetics, cells from blood and bone marrow are prepared and preserved virtually indefinitely in Carnoy's fixative (methanol/acetic acid). Numerous samples are stored unvalued in hospitals and institutes worldwide. We developed a method to analyze proteins from even a small amount of these cells by mass spectrometry using affinity chromatographic surfaces (SELDI), and demonstrated the application of proteomic biomarker research in cases of acute myeloid leukemia.