KRT7 and cancer: For the correct assessment of stromal invasion, the following 5 items are useful: (1) macroscopic or panoramic views of the histological specimen, (2) amount of fibrous components of the stroma, (3) destruction of the structure of portal tracts, (4) loss of reticulin fibers around cancer cells, and (5) CK 7 immunostaining for ductular proliferation.