Bone marrow fluorescence in situ hybridization (FISH) workup involves bone marrow sample aspiration or biopsy, treating with fluorescently labelled DNA probes targeting specific genetic abnormalities. This molecular diagnostic technique identifies and analyzes congenital abnormalities such as translocations, deletions, amplifications, and mutations in marrow cells. It helps healthcare professionals evaluate and manage hematologic malignancies such as leukemia, lymphoma, and myeloma.