For the assessment of prognostic power of PTEN immunohistochemistry we utilized a dichotomizing/binary system on the basis of two methods: A, according to published approaches, maintained PTEN expression (PTEN-normal) was assigned when PTEN expression of the tumor was similar to surrounding normal mucosa [24, 26, 28, 30], whereas PTEN loss was assigned when tumor regions had significantly lower PTEN expression than the surrounding normal mucosa (Additional file 1: Figure S1). Here, PTEN is linked to neoplasm.