Microsatellite Instability of Gastric and Colorectal Cancers as a Predictor of Synchronous Gastric or Colorectal Neoplasms

BACKGROUND/AIMS: Microsatellite instability (MSI) plays a crucial role in gastrointestinal carcinogenesis. The aim of this study was to clarify whether MSI is a useful marker for predicting synchronous gastric and colorectal neoplasms. METHODS: Consecutive patients who underwent both esophagogastroduodenoscopy and colonoscopy before the resection of gastric or colorectal cancers were included. MSI was analyzed using two mononucleotide and three dinucleotide markers. RESULTS: In total, 434 gastric cancers (372 microsatellite stability [MSS], 21 low incidence of MSI [MSI-L], and 41 high incidence of MSI [MSI-H]) and 162 colorectal cancers (138 MSS, 9 MSI-L, and 15 MSI-H) were included. Patients with MSI gastric cancer had a higher prevalence of synchronous colorectal cancer, colorectal adenoma, and gastric adenoma than those with MSS gastric cancers (4.8% vs 0.5%, p=0.023; 11.3% vs 3.2%, p=0.011; 3.2% vs 1.2%, p=0.00, respectively). The prevalence of synchronous colorectal adenomas was highest in MSI-L gastric cancers (19.0%), compared with MSI-H (7.3%) or MSS (3.2%) gastric cancers (p=0.002). In addition, there were no significant differences in the prevalence rates of synchronous colorectal adenoma among the MSI-H (13.3%), MSI-L (11.1%), and MSS (12.3%) colorectal cancers (p=0.987). CONCLUSIONS: The presence of MSI in gastric cancer may be a predictor of synchronous gastric and colorectal neoplasms, whereas MSI in colorectal cancer is not a predictor of synchronous colorectal adenoma.

Pleomorphic Xanthoastrocytoma: Report of 2 Cases

Pleomorphic xanthoastrocytoma is a recently characterized neoplasm with relatively favorable prognosis despite aggressive histological features. Two cases of pleomorphic xanthoastrocytoma involving the left temporal lobe are reported, both occurring in adolescents. The tumor is considered to arise from the subpial astrocytes of the superficial cortex. Electron microscopic examination and immunoperoxidase stains for glial fibrillary acidic protein(GFAP) are helpful in making a definitive histologic diagnosis. In contrast to malignant gliomas, pleomorphic xanthoastrocytoma does not appear to require aggressive postoperative radiation therapy or chemotherapy. Therefore, It is important to recognize and identify this type of glioma as a distinct entity.