黏膜相关淋巴组织结外边缘区淋巴瘤错配修复蛋白和微卫星表型检测的临床意义

Expression of mismatch repair proteins and microsatellite phenotypes in mucosa-associated lymphoid tissue of extranodal marginal zone lymphoma

摘要:

目的 探讨黏膜相关淋巴组织结外边缘区（extranodal marginal zone of mucosa-associated lymphoid tissue, MALT）淋巴瘤中错配修复（mismatch repair, MMR）蛋白和微卫星表型检测的意义。方法 应用免疫组化法检测40例MALT淋巴瘤（实验组）和20例良性淋巴组织增生（对照组）中MLH1、MSH2、MSH6、PMS2的表达情况。应用多重荧光PCR-毛细管电泳法检测实验组的微卫星表型，分析其与MMR蛋白的关系。结果 （1） MMR蛋白表达分为3种: 缺失（-），强弱不等阳性（+++），强阳性（+++）。MMR蛋白在实验组表达构成比差异有统计学意义（P<0.05），与MLH1[0%(-)，45%(+++)，55%(+++)]，MSH2[0%(-)，60%(+++)，40%(+++)]，PMS2[2.5%(-)，45%(+++)，52.5%(+++)]相比，MSH6[7.5%(-)，80%(+++)，12.5%(+++)]在实验组缺失率和强弱不等表达率最高。MMR蛋白在实验组有3例（7.5%）部分缺失，2例为MSH6缺失，1例为MSH6和PMS2共同缺失；在对照组有1例PMS2缺失5%（1/20），两组间比较差异无统计学意义（P>0.05）。MSH6在87.5%（35/40）实验组淋巴滤泡内存在斑驳阳性现象，在对照组淋巴滤泡内未见斑驳阳性（0%），两组免疫形态比较差异有统计学意义（P<0.05）。（2） 在实验组中，35例（87.5%）为微卫星稳定（microsatellite stability, MSS），1例（2.5%）为低频率微卫星不稳定（microsatellite instability-low, MSI-L），4例（10%）为高频率微卫星不稳定（microsatellite instability-high, MSI-H）。5例MSI中有2例MSI-H为MSH6缺失，其余3例MSI未出现MMR蛋白缺失。35例MSS中有1例为MSH6和PMS2共同缺失。（3） PCR-毛细管电泳法检测的MSI-H率（10%，4/40）高于免疫组化检测MMR蛋白缺失的检出率（7.5%，3/40），但两组比较差异无统计学意义（P>0.05），检出率一致性达92.5%（37/40）。结论 MALT淋巴瘤可检测到低频率的MSI-H表型和MMR蛋白缺失，可能具有潜在的临床意义；MSH6在MALT淋巴瘤的淋巴滤泡内存在高频斑驳阳性的免疫形态，可辅助鉴别肿瘤性淋巴滤泡。

Abstract:

Objective To investigate the expression and clinical significance of mismatch repair(MMR) protein expression and microsatellite phenotypes in mucosa-associated lymphoid tissue(MALT) of extranodal marginal zone lymphoma. Methods The expression of MMR proteins MLH1, MSH2, MSH6 and PMS2 in 40 cases of MALT lymphoma(study group) and 20 cases of benign lymphoid hyperplasia(control group) were detected by immunohistochemical method. Multiple fluorescence PCR-capillary electrophoresis was used to detect the phenotype of microsatellites in the study group, and the relationship between the microsatellite and MMR proteins was analyzed. Results The patterns of MMR protein expression were divided into three types: absence(-), unequal strength positive(+-++), strong positive(+++). The proportion of MMR protein expression in the study group was statistically significant(P<0.05). Compared with MLH1[0%(-), 45%(+-++), 55%(+++)], MSH2[0%(-), 60%(+-++), 40%(+++)] and PMS2[2.5%(-), 45%(+-++), 52.5%(+++)], the expression of MSH6[7.5%(-), 80%(+-++),12.5%(+++)] had the highest deletion rate and unequal expression rate in the study group. Partial deletion of MMR protein was observed in 3 cases(7.5%) of the study group, including 2 cases of MSH6 deletion and 1 case of both MSH6 and PMS2 deletion. In the control group, there was 1 case with PMS2 deletion(5%). There was no significant difference of the deletion rate between the two groups(P>0.05). MSH6 showed patchy positive phenomenon in 87.5%(35/40) lymphoid follicles of the study group, but no patchy positive phenomenon in the lymphoid follicles of control group(P<0.05). In the study group, 35 cases(87.5%) were microsatellite stabilization(MSS), 1 case(2.5%) was MSI-L, and 4 cases(10%) were MSI-H. MSH6 was absent in 2 of the 5 MSI cases, while no MMR protein was absent in the remaining 3 MSI cases. MSH6 and PMS2 were both absent in 1 of 35 MSS. There was no significant difference in MSI-H positive rate detected by PCR-capillary electrophoresis and immunohistochemical method [10%(4/40) vs 7.5%(3/40), P>0.05]. The consistency of detection rate of two methods was 92.5%(37/40). Conclusion Low frequency MSI-H phenotype and MMR protein deletion can be detected in MALT lymphomas, which may have potential clinical significance. MSH6 has high frequency patchy positive immunomorphology in the lymphoid follicles of MALT lymphoma, which may assist in the diagnosis of neoplastic lymphoid follicles.