OBJECTIVETo investigate the significance of bcl-10 protein expression in extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) lymphoma.

METHODSSixty-two cases of MALT lymphoma were reviewed and immunohistochemical studies for bcl-10 and Ki-67 were performed.

RESULTSSixty out of the 62 cases studied (96.8%) were positive for bcl-10. Thirty-three (53.2%) showed bcl-10 expression in both the nuclei and cytoplasm, while 27 cases (43.6%) showed only cytoplasmic staining. The 10 cases with Hashimoto's thyroiditis demonstrated bcl-10 expression in the cytoplasm. The mean age of patients with bcl-10 nuclear expression (51.4 years old) was 5.2 years younger than those (56.6 years) without bcl-10 nuclear expression. The former category also showed a male predilection (male to female ratio = 19:14, in contrast to 10:19 in the latter category). The frequency of bcl-10 nuclear expression was lower in cases from thyroid but higher in cases from lung, stomach and intestine (P < 0.05). There was no statistically significant correlation between bcl-10 nuclear expression and clinical tumor stage (P > 0.05) or tumor cell morphology (P > 0.05). Amongst the 40 cases of gastrointestinal MALT lymphoma, bcl-10 nuclear expression correlated with extent of tumor involvement. The protein was expressed in 36.4% (4 out of 11 cases) of MALT lymphoma confined to mucosa or submucosa, 65.2% (15 out of 23 cases) of those invading down to muscularis propria or subserosa, and 100% (all 6 cases) of those extending beyond serosa (P < 0.05). There was no statistically significant difference in Ki-67 proliferative index between bcl-10-positive and bcl-10-negative groups (P < 0.05). Follow-up data were available in 52 patients (83.9%) and the five-year survival rate was no statistically significant difference in survival between bcl-10-positive (29 patients, 96.3%) and bcl-10-negative groups (23 patients, 66.4%, P > 0.05).

CONCLUSIONSTwo expression patterns of bcl-10 protein were observed in MALT lymphoma: mixed nuclear-cytoplasmic and cytoplasmic only. The bcl-10 nuclear expression appears more important and correlates with anatomic site of tumor and extent of tumor involvement. Immunohistochemical detection of bcl-10 may carry some diagnostic and prognostic implications in assessment of MALT lymphoma.