The treatment outcome of gastric cancer has markedly improved with the advancement of diagnostic technology, widespread use of radical resection combined with lymph node dissection, and advances in chemotherapy. However, these results must be improved as about 700,000 people worldwide die from gastric cancer annually. Therefore, elucidation of the metastatic mechanism of gastric cancer, prevention and early detection of metastasis, and development of drugs based on the metastatic mechanism are important for achieving optimal treatment outcome.
CLINICAL FEATURES OF GASTRIC CANCER METASTASIS
There are two major forms of gastric cancer in terms of clinical metastasis. In histologically scirrhous gastric cancer, which is composed primarily of poorly differentiated adenocarcinoma/signet ring carcinoma, a large amount of interstitial component is morphologically observed, and cancer cells single-handedly assume the course of diffuse invasion. This type of gastric cancer spreads by the peritoneal or the lymph node metastatic route. In histologically nonscirrhous gastric cancer, the main presenting histological features are those of well- or moderately differentiated adenocarcinoma. In this form, cancer cells frequently invade vascular channels as tumor cell clusters (or tumor cell clumps) and spread to distant organs (hematogenous metastasis).
Lymph node metastasis is diagnosed by computed tomography, magnetic resonance imaging, endoscopic ultrasound, or positron emission tomography, but the sensitivity and specificity of these techniques are insufficient. The need for and the extent of lymph node dissection, as well as the significance of and treatment protocol for micrometastasis (MM) in lymph node metastasis, remains debatable.