Marian Stevens-Kroef studied medical biology and received her PhD from the Leiden University (Faculty of Medicine) in 1998, where she characterized chromosome 5q deletions in patients with myelodysplastic syndromes. She is specialized in cytogenetic diagnostics (karyotyping, FISH and microarray-based genomic profiling) of leukemia samples. Next to the routine diagnostics she also actively involved in improving genetic diagnostics and introducing new technologies in tumor (cyto)genetics. This has resulted in the Genome Diagnostics Nijmegen as one of the first laboratories which offers array diagnostics for hematological malignancies.
She is one of the organizers of the International workshops on cancer genetic & cytogenetic diagnostics which were held in Nijmegen and the chair of the Dutch working group of Tumor Cytogenetics (WHGD).