Immunohistochemical staining of SNAIL & SLUG (A, B) and ZEB1 (C, D). (A) In the center of tumor, SNAIL & SLUG is negative in both stromal cells and tumor. (B) The nuclear staining of SNAIL & SLUG is positive in tumor cells in tumor margin. (C) ZEB1 positive stromal cell are mostly observed in tumor center. (D) In tumor margin, ZEB1 is positive in tumor cells (marked with arrow), as well as in stromal cells.