KRT5 and in situ carcinoma: Squamous cell carcinoma can, to some extents, shows epithelioid and spindle cells but generally exists carcinoma in situ at peripheral surface epithelium, although rare cases express Myogenin protein, but they usually display strongly positive for CK5/6, p63 and p40, and are negative for Desmin and Myo-D1 [69].