Microsatellite instability in solitary and sporadic gastric cancer.
Recently, the presence of microsatellite instability (MSI) has been reported in gastric cancer and associated with older age of presentation, distal tumor location, early disease staging, and better overall prognosis. Different characteristics in presentation and in tumor behavior may be explained by different genetic alterations during carcinogenesis of gastric cancer. Identification of specific genetic pathways in gastric cancer may have direct impact on prognosis and selection of treatment strategies.


METHODS
All 24 patients were treated by radical surgery. Fragments of normal and tumor tissues were extracted from the specimen and stored at -80 degrees C before DNA purification and extraction. PCR amplification utilizing microsatellite markers was performed. Tumors presenting PCR products of abnormal sizes were considered positive for microsatellite instability (MSI+).


RESULTS
Five patients (21%) had tumors that were MSI+ in at least 1 marker. In the group of patients with Lauren's intestinal-type gastric carcinoma, 3 had tumors that were MSI+ (23%), while in the group of diffuse-type gastric cancer, 2 patients had tumors that were MSI+ (19%). The mean age of presentation and the male:female ratio was similar in both groups. Tumors that were MSI+ were more frequently located in proximal portion of the stomach compared to microsatellite-stable (MSS) tumors (40% vs. 16%). Although there was a trend of patients with MSI+ tumors towards a proximal gastric tumor location, early staging, and negative lymph node metastasis, there was no statistical significance compared to those with MSS tumors (P >.1). Comparison of overall and disease-free survival between gastric tumors that were MSI+ and those that were MSS found no statistically significant differences (P >.1).


CONCLUSIONS
Microsatellite instability is a frequent event in gastric carcinogenesis and shows a trend towards distinct clinical and pathological characteristics of gastric cancer.
Perez
Rodrigo Oliva
RO
Disciplines of Surgery of the Digestive Tract and Coloproctology, Hospital das Clínicas, Faculty of Medicine, University of São Paulo - São Paulo/SP, Brazil.
Jacob
Carlos Eduardo
CE
D'Ottaviano
Fabricio L'ofreddo
FL
Alvarenga
Conrado
C
Ribeiro
Adriana Safatle
AS
Ribeiro
Ulysses
U
Bresciani
Cláudio José Caldas
CJ
Zilberstein
Bruno
B
Krieger
José Eduardo
JE
Habr-Gama
Angelita
A
Gama-Rodrigues
Joaquim José
JJ
D000230:Adenocarcinoma / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil / Q000453:epidemiology; D018572:Disease-Free Survival; D005260:Female; D005819:Genetic Markers; D042822:Genomic Instability; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D009367:Neoplasm Staging; D013274:Stomach Neoplasms / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D016019:Survival Analysis
D005819:Genetic Markers