Molecular analysis of gastric washings in the diagnosis and monitoring of gastric lymphomas

The monitoring of gastric lymphomas is often hampered by the inherently limited sampling provided by small endoscopic biopsy specimens. To investigate the feasibility of using gastric washing fluid for monitoring patients with known gastric lymphoma and for diagnosing gastric involvement in patients with extranodal nongastric lymphoma, we collected 49 gastric washings from 39 patients (29 patients with gastric lymphoma and 10 patients with nongastric extranodal lymphoma). Collection was done at the time of follow-up biopsy and when no endoscopic abnormalities were found. DNA was extracted from the washing fluid and analyzed for clonal IgH gene rearrangement by Southern blotting (J6 probe) and/or polymerase chain reaction (PCR) (using VH-FR3 and JH primers). Forty-one of 49 samples (84%) yielded sufficient DNA for molecular analysis. Sixteen of 41 analyzable gastric washing samples (39%) failed Southern blot analysis due to degraded or insufficient DNA. Concordance between the results of Southern blot analysis of the washing and histology of the simultaneous biopsy specimen was found in 20 (80%) of the remaining 25 samples. The IgH PCR result was concordant with biopsy histology in 33 out of 41 washing samples (80%). The overall concordance between molecular clonality studies of washings (Southern blotting and/or PCR) and biopsy histology was 83% (34 of 41). Of the 7 (18%) discrepant specimens, 2 were diagnosed histologically as lymphoma, but the simultaneous washings were negative by molecular studies. Five biopsy specimens were histologically benign, but the corresponding washings demonstrated clonal IgH gene rearrangement (3 cases by PCR and 2 cases by Southern blotting). This study demonstrates the diagnostic utility of molecular clonality analysis of gastric washings.