The Leucine-rich repeats and immunoglobulin-like domains-2 (LRIG2) gene expression in pituitary adenoma and its correlation with tumor invasiveness were studied. The expression of LRIG2 mRNA and protein in human pituitary adenoma obtained surgically was detected by RT-PCR (39 cases) and immunohistochemical staining (30 cases). It was found that LRIG2 was mostly localized at the nucleus of the pituitary adenoma cells. Its expression was significantly higher in the invasive cases than in the non-invasive cases. LRIG2 protein was positive in 14 cases out of 21 cases of invasive adenoma, but only 2 cases were positive in 9 cases of non-invasive adenoma. The positive expression rate of LRIG2 mRNA was 91.3% in invasive cases (total 23 cases) and 62.5% in non-invasive cases (total 16 cases), respectively. LRIG2 gene is overexpressed in invasive pituitary adenoma. It may play an important role in pituitary adenoma invasiveness and further studies are necessary to elucidate the mechanism under this phenomenon.