PCR-based clonality analysis: a reliable method for the diagnosis and follow-up monitoring of conservatively treated gastric B-cell MALT lymphomas?
We evaluated polymerase chain reaction (PCR) amplification of specific immunoglobulin heavy chain (IgH) gene rearrangements as a means of demonstrating monoclonality during follow-up of conservatively treated gastric MALT lymphoma, and compared the reproducibility of PCR on sequential frozen and paraffin-embedded endoscopic biopsies. We established an association between clonality detected by PCR and the histological observations. Sixty-nine pairs of sequential frozen and paraffin-embedded endoscopic biopsies from 21 conservatively treated patients were graded according to the Wotherspoon-Isaacson histological scoring system, which provides a measure of diagnostic confidence on a scale 0-5. PCR amplification of the IgH gene was performed using FR3/JH and FR2/JH primers. 68/69 paired samples (98.5%) showed identical mono- or polyclonal PCR amplification patterns. Forty-seven out of 48 pairs of samples sharing similar histological features produced identical amplification patterns in both fresh and paraffin-embedded tissues. In comparison with the histological grading, monoclonality was detected in 64.2% and 41.6% of samples scored 5 and 4, respectively. Conversely, among 64 samples scored 0-3, a monoclonal pattern was observed only in two samples, one of which was from a patient who relapsed 9 months later. PCR-based clonality analysis by demonstration of specific IgH gene rearrangement can be easily and reliably performed on both frozen and paraffin-embedded endoscopic biopsies. In conjunction with histological observation, this method can be used as a complementary tool to monitor MALT lymphoma regression during conservative treatment.