INTRODUCTION
Endometrial cancer is the second common tumor in the female reproductive system worldwide with an increasing mortality due to the epidemic of obesity and the resulting hyperinsulinemia (1, 2). The early detection of this cancer and precancerous change plays an important role in reducing mortality and improving survival rate. In recent years, endometrial cytology test has become a new direction in the screening of endometrial cancer and precancerous change due to low trauma, convenient operation, economic efficiency, and high safety (3).The common devices to collect endometrial cells contain Li Brush, SAP-1, Pippelle, Tao Brush, and so on (4, 5).
Haematoxylin and eosin (H-E) stain is the most basic and widely pathological method used in cytological and histological diagnosis. It can be used to visualize the cellular morphology and structures of different composition excellently, especially in differentiating nucleus from cytoplasm, even if under low magnification (6-8). Hematoxylin is a basophilic dye that turns cell nucleus into blue-purple, and eosin is an acidic dye that turns cell cytoplasm, collagen, and erythrocytes into red-pink (9). The two dyes are combined in sequence for abundant contrast between the cellular components (10, 11). H-E stain is easily implemented, inexpensive, reliable and informative (12).This stained slides can be kept many years without fading due to its better stability (8). However, it is difficult to differentiate amyloid, muscle, keratin and other extracellular and intracellular secretions which are all eosinophilic (13).
Papanicolaou stain is commonly used in identification of cytological smears, which improves the visualization of nuclear and cytoplasmic morphology (12, 14, 15). It can assess pivotal cellular features, including nuclear chromatin alterations, cytoplasmic structures, especially in maturing squamous epithelial cells. Papanicolaou stain is also performed in detecting the degrees of cellular degeneration or necrosis, and the production of mucin, glycogen, and keratin (14, 16, 17). In recent studies, Papanicolaou stain has been confirmed validly and widely in the detection of cervical cells (18, 19).Though this method was not originally designed for endometrial cancer, some researchers tried to modify this stain to improve the detective rate of endometrial lesions (20). The disadvantages of Papanicolaou stain contain time-consuming, complicated procedure and additional wet fixation (21, 22).
Although both methods could be applied to staining endometrial cells (23-25), no research was published to compare the effects. In this study, we distinguished the difference between H-E and Papanicolaou stain through the semi-quantitative scoring system in endometrial cytology ( Table S1) (24).