Laminin-5 (γ2 chain) is a marker of invading cancer cells in human gallbladder carcinoma: Special emphasis on extension of carcinoma in situ along Rokitansky-Aschoff sinuses

Gallbladder carcinoma (GC) is a relatively uncommon malignancy and is often caused by diagnostic difficulties in distinguishing the extension of carcinoma in situ (CIS) from invasive carcinoma along Rokitansky-Aschoff sinuses (RAS). The laminin-5, a heterotrimer, is composed of α-3, s-3 and γ-2 chains. The γ-2 chain is expressed in various invasive carcinoma cells. There are numerous reports that have described that laminin-5-γ-2 is associated with tissue invasion in many organs. However, few studies are found in gallbladder carcinoma. To clarify the relationship between laminin-5-γ-2 chain (LN-5) expression and the development of GCs, we performed an immunohistochemical study of 93 GCs. Cases were classified into three groups: CIS with/without the extension along RAS (Group A; n=17), carcinoma invading mucosa or muscular layer (Group B; n=5) and carcinoma invading beyond perimuscular connective tissue (Group C; n=71). The immunohistochemical intracytoplasmic expression was detected in the invasive fronts of the tumor. In the invasive components of Group B and C, LN-5 was expressed in 100 and 97% of cases, respectively, whereas in the CIS lesions of GCs, expression was not observed in Group A. LN-5 expression in the GCs tended to increase as tumors developed, which may be an indicator of the potential invasiveness of the tumor. Our results indicate that, in GCs, a strong intracytoplasmic expression of LN-5 was identified in the cancer cells whether in situ they extend along RAS or invading stroma.