Immunohistochemistry of gastric stromal tumors

It is well known that gastric stromal tumor immunohistochemistry belongs to the digestive system tumor. Data show that gastric stromal tumor immunohistochemistry is one of the main gastrointestinal diseases that threaten the health of Chinese people. The scary thing about immunohistochemistry of gastric stromal tumor is that it is difficult to detect this disease in time through traditional diagnostic methods, which can easily delay the best treatment. So what exactly is gastric stromal tumor immunohistochemistry and what kind of disease is it?

Gastrointestinal stromal tumor (GIST) is a common digestive system tumor in my country. As most tumor cells are undifferentiated or epithelioid, traditional detection is often inadequate and may lead to missed or misdiagnosed clinical test results, resulting in inappropriate treatment options [1]. With the continuous advancement of high-resolution electron microscopy, molecular biology, and immunohistochemical counting, we have carried out targeted pathological and immunohistochemical observations of gastrointestinal stromal tumors, as reported below.

1 Materials and methods

1.1 General Information

A total of 60 GIST patients admitted to our hospital from July 2015 to June 2017 were selected as the research subjects. They were aged 28 to 72 years old and had varying degrees of clinical symptoms such as abdominal distension and pain, masses, intestinal obstruction, and bloody stools. Clinical imaging (B-ultrasound, CT) examinations showed substantial mass in the abdominal cavity. All patients were confirmed to have GIST by postoperative pathology and had not received any radiotherapy or chemotherapy before surgery. According to the risk classification of the National Institutes of Health (NIH) of the United States [2], there were 11 cases of high risk, 15 cases of intermediate risk, 28 cases of low risk, and 6 cases of very low risk. Among the 60 patients, there were 34 males and 26 females with an average age of (44.82±9.91) years, weight of 49-87 kg (average of (63.28±8.94) kg), disease course of 15 days to 2 years (average of (1.16±0.51) years), and tumor location: stomach in 35 cases, small intestine in 15 cases, colorectum in 6 cases, and esophagus in 4 cases. All patients were informed of this study and their relatives provided informed consent.

1.2 Methods

The gross specimen characteristics were observed with the naked eye, the tumor cell manifestations and pathological characteristics were observed under the microscope, and the pathological specimens were collected for laboratory fixation. The fixative solution was 10% neutral formalin, and the specimens were routinely paraffin-embedded, serially sectioned and divided into two equal parts. One part was subjected to routine hematoxylin-eosin (HE) staining analysis for pathological examination; the other part was tested for the positive expression of tumor cells (CD117), type i transmembrane glycoprotein molecules (CD34), SMA, Ki67, and S100 protein molecules in the specimens using immunohistochemistry and ready-to-use reagents.

1.3 Positive judgment

Immunophenotyping of CD117, CD34, SMA, S100, and Ki67 positivity[3]: CD117 was recorded as positive if the cells stained in the cytoplasm of the tumor cells; CD34 was recorded as positive if the cells stained in the capsule of the tumor cells; SMA was recorded as positive if the cells were brown-yellow, the cytoplasm was stained, and the positive expression area was greater than 20% after staining; S100 was recorded as positive if the nucleus was stained after staining; each section was placed under a high-power microscope for positive cell observation, and 10 fields of view with clear positive cell staining and low background staining were randomly selected. The number of positive cells in each field of view was observed and counted. A positive cell number greater than 5% was considered Ki67 positive, otherwise it was considered negative.

1.4 Statistical analysis

SPSS 19.0 software was used to perform statistical analysis on the data of this study. n or % represents count data, and the X2 test was used. The mean ± standard deviation ( ±s) represents measurement data, and the t test was used. P < 0.05 was considered statistically significant.

2 Results

2.1 Characteristics of Gastrointestinal Stromal Tumors

Macroscopic observation of the specimens revealed tumors with diameters ranging from 0.7 to 10.8 cm, which were mainly located in the basal and inferior layers of the mucosa, on the mesentery, and outside the serosa. All tumors had clear boundaries and hard texture. The woven cross-section was mainly red, white or grayish white (grayish yellow) with clear boundaries. There were obvious ulcers and erosions on the surface of the tumor, as well as necrosis and cystic lesions. Among them, 34 patients with low- and very low-risk GIST had tumors that grew in an expansive manner in the digestive tract with clear boundaries, no capsule, and some with pseudocapsules. The cross-section was tough, mainly grayish white, and partially grayish red. The tumors of 26 patients with intermediate- and high-risk GIST were polyp-like, soft in texture, with bleeding, necrosis, and cystic lesions.

Microscopic observation of the pathological specimens showed that the tumor cells mostly grew in an expansive manner in the muscular layer of the digestive tract, and locally showed invasive growth with their edges crossing between smooth muscles. The cell types were mainly round, spindle-shaped, epithelial-like or mixed, with unclear boundaries, and the cytoplasm was moderately to slightly eosinophilic, with spindle-shaped or oval nuclei, thin membranes, and relatively uniform chromatin. Small nucleoli and large areas of tumor cells or some foci within the tumor showed coagulative necrosis, and the cell shadows presented were homogeneously stained red, and were also presented by residual nuclear fragments.

Among the 60 GIST patients, 5 cases (8.33%) had round cell type, 37 cases (61.67%) had spindle cell type, 17 cases (28.33%) had epithelioid cell type, and 7 cases (11.67%) had mixed cell type.

2.2 Immunohistochemical analysis

Among the 60 GIST patients, the positive expression results of CD117, CD34, SMA, S100, and Ki67 were 55 cases (91.67%), 50 cases (83.33%), 17 cases (28.33%), 22 cases (36.67%), and 22 cases (36.67%), respectively. Among them, 43 cases (71.67%) showed positive expression of both CD117 and CD34. Among the 22 patients with Ki67 positive expression, the rates of high, moderate, low and very low invasion risk were 8 (72.73%), 6 (40.00%), 7 (25.00%) and 1 (16.67%), respectively. The differences among the groups were statistically significant (P<0.05). See Table 1 and Table 2.

Figure 1 CD34 Figure 2 CD117

3 Discussion

GIST is a relatively common tumor in clinical practice. Its lesions may extend from the esophagus to the rectum, with the stomach and small intestine being the most common. Due to the special characteristics of GIST tumor cells and their wide range of locations, the clinical manifestations of patients have strong individual differences and are non-specific, which makes preoperative diagnosis more difficult[4]. The pathological examination results in this study showed that GIST cells not only had obvious volume differences but also had clear boundaries, but we also noticed that although the surface was smooth, the fibrous capsule was not obvious and may be accompanied by various types of degeneration and necrosis. However, if GIST is a higher degree of malignancy, its main manifestations are blurred boundaries and soft texture, often appearing like fish meat, and some even have inflammatory adhesions at the junction with surrounding normal tissues.

In addition, immunohistochemistry results showed that the positive expression of CD117, CD34, SMA, S100, and Ki67 in 60 GIST patients exceeded 28%, and among the 22 patients with Ki67 positive expression, there were significant differences among the groups with high, moderate, low, and very low risk of invasion. These results suggest that GIST has a stronger proliferative potential as the risk of stromal tumors increases, and that the differentiation type of the tumor is not directional [5]. Based on this, we consider that Ki67 can be used as a reference for the diagnosis of benign or malignant GIST in clinical testing. Qin Shuangli et al. [6] also mentioned in the literature that Ki67 is a nuclear antigen associated with proliferating cells, and its expression level is closely related to the proliferation activity of tumor cells. Based on this, we believe that it can be used as a common detection item for the biological behavior and prognosis of tumors.

In summary, the positive expression of tumor cells and type i transmembrane glycoprotein molecules can be used as the basis for the diagnosis of clinical gastrointestinal stromal tumors. Further immunohistochemical staining can improve the judgment and is of great significance for the confirmation of GIST tumor cells.