Combined histology and molecular biology for diagnosis of early stage gastric MALT lymphoma.

OBJECTIVE

To establish a sequential diagnostic procedure of gastric mucosa-associated lymphoid tissue (MALT) lymphoma and provide evidence for selected optimal cases to be treated in the early stage.

METHODS

Thirty-one cases of gastric lymphoid hyperplasia (GLH) were selected and multiple investigations including histology, protein level, DNA and chromosome levels, combined with clinical follow-up were performed. Histological grade was according to Isaacson's criteria of GLH; CD20, UCHL-1 (CD45RO), anti-kappa (kappa), anti-lambda (lambda) and Ki-67 were used for immunohistochemical staining; semi-nested polymerase chain reaction (PCR) was used to detect IgH gene rearrangement and reverse-transcription PCR (RT-PCR) was used to detect API2-MALT1 fusion of the chromosome translocation t(11;18)(q21;q21). Twenty-nine cases underwent eradication therapy for Helicobacter pylori. Changes in histological grade, endoscopic appearance, expression of Ki-67 and IgH gene rearrangement were compared after eradication treatment.

RESULTS

Of the 31 cases of GLH with predominant chronic gastritis and gastric ulcer most were histological grade 2 and 3. Only one case had lambda light chain restriction and 10 cases had monoclonal IgH gene rearrangement. Expression of Ki-67 and monoclonal IgH gene rearrangement were significantly increased with increased lymphoid hyperplasia (P < 0.05). Two cases had API2-MALT1 fusion. Helicobacter pylori was eradicated in 25 cases and another course of treatment had to be given in 4 cases. All cases were followed up for 1.5-37 months. Of the 27 successful eradication cases, 18 showed complete regression both histologically and endoscopically, 4 had partial regression and 7 were unchanged.

CONCLUSIONS

A sequential diagnostic procedure based on histology, expression of Ki-67 combined with clonality of IgH rearrangement and API2-MALT1 fusion helps to diagnosis of early stage gastric MALT lymphoma and choose the best treatment strategy.