Among the gastrointestinal mesenchymal tumors, GISTs and GILs were the most common submucosal lesions worldwide.23 They could happen anywhere in the digestive tract and GISTs possessed malignant transformation potence, whereas, GILs were benign lesion, the difference in size and shape of them were significant, and the incidence was not associated with age or sex. With the increasing update of detection technologies, endoscopic ultrasonography (EUS) and computed tomography (CT) were always the dominated detection methods, even combined with AI-assisted diagnostic technology.24 The pathological diagnosis was usually made by IHC methods and genetic tests,25 however, the economic and time cost were relatively higher. Nowadays, the incidence of GISTs and GILs was still increasing, the morbidity were 34.2% (39/114) and 65.8% (75/114) in our current research, respectively, new GISTs and GILs cases are still on the rise, thus, timely and accurate diagnosis is particularly important for treatment, the primary treatment option has always been surgical removal,26 whereas, the GISTs had postoperative recurrence risk.
4.1 The basic principle of special stains to identify different components
In the present study, a new detection technique, special stains, was used to distinguish GISTs and GILs, which was easily overlooked, because of IHC analysis and molecular examinations were the dominanted methods. On account of the main components of GISTs (collagen fibers secreted by stromal cells) and GILs (smooth muscle fibers) were significant different, which were rarely reported in domestic and foreign researches, special stain technology was to dye different components into different colors by the specific adsorption of different stains to distinguish them, and there is no report at home or abroad about this new finds from the daily pathological diagnosis.
4.1.1 The basic principle of MT stain MT stain was related to the size of anionic dye molecules and tissue penetration: small molecular weight like ponceau dye, can easily penetrate the dense structure and low permeability of the tissue to be red, like muscle fibers, while large molecular weight can only enter the loose structure and high permeability of the tissue such as collagen fibers. On account of the molecular weight of aniline blue was very large, and contained alkaline amino acids, the collagen fibers appeared blue by aniline blue of MT stain. Consequently, the end results were that 92.3% (36/39) GISTs were stained blue and 97.3% (73/75) GILs were stained red (P < 0.01), individual differences in results were due to collagen fibrogenesis or collagen fibrogenesis. To sum up, GISTs were mainly composed of stromal cells, which can secrete both collagen fibers and muscle fibers and ultimately lead to the particularity of individual cases.
4.1.2 The basic principle of AB-PAS stain AB-PAS stain was a method to detect the distribution and content of glycogen in cells, the dyeing principle was that AB-PAS stain consisted of Alcian Blue and Periodic Acid-Schiff (PAS) stain. Alcian Blue was an acidic stain mainly used to stain acidic polysaccharides such as heparin sulfate and acid mucopolysaccharide. PAS stain was a selective stain method used to detect the presence of glycogen in tissues. Because GILs were rich in smooth muscle, and their contraction requires the consumption of a lot of energy released by glycogen, the glycogen rich in them can eventually be stained rose red by AB-PAS, it was verified by PAS and D-PAS stain, showed in figure S1. Consequently, AB-PAS stain positive 100% (75/75) (P < 0.01) in GILs cases, in contrast, GISTs were AB-PAS negative (light purple) for all the cases studied. It should be added that the special stain results were consistent between GISTs in different parts of the digestive tract, and the special stain results were also consistent between GILs in different parts of the digestive tract.
4.1.3 The basic principle of W-G stain W-G stain was a modified Romanowsky staining technique used to stain blood and bone marrow smears. Cell staining involves physical adsorption and chemical affinity that allows the stain to penetrate and remain inside the cell. Due to the different chemical composition of each cell and its components, their affinity for acidic staining (eosin) and basic staining (methylene blue) for this kit varies greatly. In this study, there was no significant difference in staining between GISTs and GILs, but it could stain mast cells and distinguish between tumor and non-tumor stroma.
4.2 In conclusion
To sum up this retrospective study present a new method for the specific differentiation of GISTs and GILs, MT and AB-PAS stains could also differentiate these two tumors, furthermore, AB-PAS stain was more sensitive and more specific, which were also confirmed in the detection of new GIST and GIL cases in supplementary material table 2. The research achievement could provide more cost-effective, simple, and high sensitivity and specificity inspection methods, which may instead of IHC analysis in the future, especially in resource-limited grass-roots testing institution, that is, MT and AB-PAS (much more specificity) could be a pre-diagnosis of GISTs and GILs in the absence of immunohistochemical conditions, the diagnostic flow chart showed as figure 6, it should be noted that the ultimate accurate diagnosis should must combine with clinical signs and symptoms.
In spite of this study presents a new detection method for the identification of GISTs and GILs, after all, this is only a retrospective study, the conclusion still needs to be further verified in daily work until it became a commonly used clinical diagnostic method. In the future, special stain technology will be combined with artificial intelligence assisted diagnosis technology to contribute to the precision diagnosis and treatment of gastrointestinal tumors.