Fig. 3

A low-power view of the tumor tissue by surgical resection reveals that the tumor cells are mainly located in the lamina propria and seem to be transitional with the surface mucosa (arrows) and infiltrates the muscular layer (a), The tumor cells are negative for CK staining (b) and diffusely positive for CD21 (c, f) by immunohistochemistry. The tumor cells are round, oval or polygonal with indistinct cellular borders and sprinkled with small lymphocyte infiltration, part of which had a syncytial-like appearance (d). Atypical mitoses are frequently observed (e, arrows)