Lymphatic Metastasis
Malignant gastric tumors preferentially spread via the lymphatic system. Tumor cell migration along lymphatic vessels can occur in two directions: orthograde (in the direction of normal lymphatic flow) and retrograde (against the normal flow).
Regional lymph nodes are the first barrier encountered by the tumor. They are located along the lesser and greater curvatures of the stomach, taking the primary impact during orthograde metastasis.
Distant retrograde deposits are of special diagnostic significance in pathology. Their detection is often the key to establishing the diagnosis:
- Virchow's node — involvement of the left supraclavicular lymph node.
- Krukenberg tumor — specific metastatic involvement of the ovaries.
- Schnitzler's metastasis — tumor cell proliferation in the rectouterine pouch (Douglas pouch) or pararectal fat.
Hematogenous and Implantation Pathways
In addition to the lymphatic system, gastric cancer actively utilizes the bloodstream. Hematogenous metastasis leads to secondary tumor foci in distant organs. The liver is the most frequent target, accessed via vessels of the hepatogastric ligament. Hematogenous deposits are also found in bone tissue, brain structures, and the skin.
The third pathway is implantation (or transcoelomic contact spread). This occurs when the tumor breaches the organ wall. Tumor cells disseminate throughout the peritoneal cavity and settle on serous membranes. This process inevitably leads to peritoneal carcinomatosis.
Pathomorphology and Invasive Growth
To study the histological picture of gastric cancer, tissue sections are conventionally stained with hematoxylin and eosin (H&E). A well-differentiated tubular adenocarcinoma serves as a classic example.
The main morphological criterion of malignancy here is invasive growth. Under the microscope, atypical glandular complexes are clearly visible destroying normal histoarchitecture and aggressively invading the muscularis mucosae.
Cellular and Tissue Atypia
Malignant transformation is accompanied by profound changes at the cellular and tissue levels.
Cellular changes are characterized by marked atypia: normal cell architecture is grossly disrupted. High mitotic activity is observed. Numerous mitotic figures appear in the field of view, among which atypical mitoses—pathological forms of division specific to malignant growth—attract special attention.
Tissue changes manifest as the loss of normal glandular differentiation. This is expressed by the fusion of glands with one another and the complete disappearance of their lumens. Against the background of these structural breakdowns, signs of cellular atypia become even more evident, forming the classic picture of a malignant tumor.