Pink-color sign in esophageal squamous neoplasia, and speculation regarding the underlying mechanism

Figure 1 Histologic findings of esophageal lesions. A: Esophageal lesion with keratinous layers, shown by black parentheses; B: Esophageal lesion without keratinous layers.

Figure 2 Endoscopic image of type IIc esophageal cancer. A: Endoscopic image of type IIc esophageal cancer immediately after iodine staining; B: Endoscopic image of type IIc esophageal cancer 2 min after iodine staining. The pink-color sign is observed on the right side of the lesion; C: Endoscopic image of type IIc esophageal cancer 3 min after sodium thiosulfate spraying.

Figure 3 A small region of interest was chosen in both the pink-color sign positive and pink-color sign negative areas. These regions of interest were carefully chosen to be of similar size in each area. The red-green-blue components of each region of interest were calculated using Image J software.

Figure 4 The U’ and V’ values of the pink-color sign positive mucosa and negative mucosa in the early, late and final phases were plotted on a color diagram. A: Pink-color sign positive mucosa; B: Pink-color sign negative mucosa.

Figure 5 Mean U’ and V’ values of the mucosa in the early, late and final phases were plotted on a color diagram. A: Pink-color sign positive mucosa had a lower mean V’ value in the late phase (pinkish color) than in the early phase (yellowish color), suggesting that the pink-color sign positive mucosa underwent a color change from yellow to pink. The mucosa had similar mean U’ and V’ values in the late and final phases, suggesting that the color of pink-color sign positive mucosa in the late stage was similar to the color of mucosa after complete fading of iodine staining; B: Pink-color sign negative mucosa had similar mean U’ and V’ values in the early and late phases (yellowish color), suggesting that pink-color sign negative mucosa did not change in color during this time period.

Figure 6 Speculated mechanism of the pink-color sign.