DETECTION OF APOPTOTIC CELLS IN CYTOLOGY SPECIMENS - AN APPLICATION OF TDT-MEDIATED DUTP-BIOTIN NICK END LABELING TO CELL SMEARS

We applied TdT-mediated deoxyuridine triphosphate (dUTP)-biotin nick e nd labeling (TUNEL) to cytologic smears in order to detect the cells u ndergoing apoptosis. These smears were obtained by scraping the cut su rface of 9 cases of carcinoma, including renal-cell carcinoma (3 cases ), esophageal squamous-cell carcinoma (3 cases), and gastric adenocarc inoma (3 cases), and were fixed and prepared by different methods. The results were also compared with those of tissue sections. TUNEL in sm ears was generally associated with higher background nuclear stain tha n in tissue sections. Smears that were fixed in 4% or 8% paraform alde hyde or absolute methanol exhibited results comparable with those of t issue sections, with minimum background in all cases examined. There w ere no significant differences in TUNEL labeling index among tissue se ctions and smears fixed in 4% or 8% paraformaldehyde or in absolute me thanol. Smears treated in Carnoy's fixative (3:1 methanol:acetic acid) and air-dried smears demonstrated a higher background. TUNEL positivi ty could not be detected in slides decolorized from May-Grunwald-Giems a stain. Markedly high background which may occur as a result of artif actural DNA breaks, was also observed in slides decolorized from Papan icolaou stain, in which TUNEL-positive cells could be evaluated only i n 3/8 cases. Application of the TUNEL method to cytology specimens has disadvantages or limitations compared to its application to histologi cal sections, bur the method is considered the most suitable one for d etecting cells undergoing apoptosis in cytology materials. (C) 1998 Wi ley-Liss, Inc.