Rare Histological Types of Malignant Gastric Neoplasms: Features of Histomorphological and Visual Structure

Diagnosing rare histological types of malignant gastric neoplasms causes difficulty due to the nature of tumor growth, the lack of clear cellular differentiation and an extremely rare incidence. The aim of the study is to increase the accuracy of diagnosing rare types of malignant gastric neoplasms using modern methods of radiation diagnosis, depending on their histological characteristics. Materials and methods. The authors examined the data of patients with malignant gastric neoplasms of epithelial (N1, n = 385) and non-epithelial origin – gastrointestinal stromal tumor of the stomach (N2, n = 27), who were diagnosed and (or) treated at the BI «Republican Clinical Oncological Dispensary» under the Health Ministry of Chuvashia and the BI «City Clinical Hospital No. 1» under the Health Ministry of Chuvashia in 2022-2023. The control group is N3 (n = 40). A comparative analysis of data obtained by instrumental diagnostic methods (computed tomography, ultrasound) with a histomorphological description was carried out. Results. Rare histological types of gastric malignancies were identified: gastrointestinal stromal tumor in 6.6% (n = 27), neuroendocrine neoplasias in 3.6% (n = 15), undifferentiated cancer in 3.4% (n = 14), squamous cell carcinoma of the gastric cardia made 2.4% (n = 10). Gastrointestinal stromal tumor, neuroendocrine neoplasias and undifferentiated cancer were predominantly found in the body of the stomach (70.4%, 73.3% and 35.7%, respectively). Squamous cell carcinoma was found exclusively in the gastric cardia, involving the cardioesophageal junction (below the Z-line by 2 cm). G astrointestinal stromal tumor in 55.5% of cases was diagnosed as having a low risk of the disease progression. Neuroendocrine gastric neoplasias in 60% of cases had a low degree of tumor malignancy, and squamous-cell carcinoma of gastric cardia in 60% of cases had an intermediate degree of malignancy. In undifferentiated gastric cancer, cellular differentiation of the tumor was lost. A combined use of radiation diagnostic methods increased their informative value in identifying rare histological types of gastric malignancies: sensitivity – 95.5%, specificity – 98.5%, accuracy – 98.1%. Conclusions. A complex use of radiation examination methods increased the diagnostic accuracy of rare histological types of malignant gastric neoplasms.