Fluorescent in situ hybridization for identifying cytogenetic abnormalities in inadequate and suboptimal specimens.

Conventional cytogenetic analysis is often hampered by its dependency on the evaluation of dividing cells. When the mitotic index is low, or the cytogenetic preparation suboptimal, an accurate diagnosis often cannot be achieved using standard GTG banding. Molecular cytogenetics using fluorescent in situ hybridization (FISH) can be extremely useful in such a situation because it can be performed on nondividing interphase nuclei, and can usually be carried out on existing slides without requiring an additional specimen. The present paper presents two case histories to illustrate the utility of FISH in the clinical setting.