Perimuscular connective tissue contains more and larger lymphatic vessels than the shallower layers in human gallbladders

摘要

AIM: To clarify whether perimuscular connective tissuecontains more lymphatic vessels than the shallowerlayers in human gallbladders.METHODS: Lymphatic vessels were stainedimmunohistochemically with monoclonal antibody D2-40,which is a specific marker of lymphatic endothelium, inrepresentative sections of 12 normal human gallbladdersobtained at the time of resection for colorectal carcinomaliver metastases. In individual gallbladder specimens,nine high-power (× 200) fields with the highestlymphatic vessel density (LVD), termed "hot spots", wereidentified for each layer (mucosa, muscle layer, andperimuscular connective tissue). In individual hot spots,the LVD and relative lymphatic vessel area (LVA) weremeasured microscopically using a computer-aided imageanalysis system. The mean LVD and LVA values for thenine hot spots in each layer were used for statisticalanalyses.RESULTS: In the mucosa, muscle layer, andperimuscular connective tissue, the LVD was 16.1 ± 9.2,35.4 ± 15.7, and 65.5 ± 12.2, respectively, and the LVAwas 0.4 ± 0.4, 2.1 ± 1.1, and 9.4 ± 2.6, respectively.Thus, both the LVD and LVA differed significantly (P <0.001 and P < 0.001, respectively; Kruskal-Wallis test)among the individual layers of the wall of the gallbladder,with the highest LVD and LVA values in the perimuscularconnective tissue. Most (98 of 108) of the hot spotswithin the perimuscular connective tissue were locatedwithin 500 μm of the lower border of the muscle layer.CONCLUSION: The perimuscular connective tissuecontains more and larger lymphatic vessels than the shallower layers in the human gallbladder. This observation partly explains why the incidence of lymph node metastasis is high in T2 (tumor invading the perimuscular connective tissue) or more advanced gallbladder carcinoma.