There is no alteration of cellular polarity, little or no cytologic atypia, and infrequent mitoses which, if present, are usually basally located.

• 此肿瘤上皮增生整齐，增生至6层或更多，伴纤维血管轴心，上皮细胞极性没有改变，细胞无或少见不典型性，核分裂少见，如果出现，通常也只是在基底层。