Reserve cells, which are capable of undergoing both columnar and squamous differentiation, may be candidate progenitor cells for the formation of these combined lesions.10, 19, 39 This view is supported by the observation that, in incidental cases of lesions with coexisting AIS and SIL, K17‐positive reserve cells were found to be p16‐positive and HPV‐positive.10 Here, KRT17 is linked to squamous cell intraepithelial neoplasia.