SCCIS of the skin and DCIS of the breast are well-known lesions that have been described for what they are. The histopathologic diagnosis of these lesions is straightforward and repeatable. It is clear that so-called colonic adenoma, CIS of the skin, and CIS of the breast are all malignant neoplastic processes confined in their epithelium of origin. As one can see from the histopathologic comparison of these lesions in the present study, many, if not all, of the histopathologic attributes—such as lack or decrease of maturation, increase of nuclear size, increase of nucleus to cytoplasm ratio, hyperchromasia, heterochromasia, increase of mitotic activity, and presence of necrosis—used in diagnosis of CIS of the skin and of the breast are evident in the so-called colonic adenoma. This further reinforces our previous conclusion stated in Part III of this study that the so-called colonic adenoma is not adenoma, but CIS. [3]

In addition, from the comparison, it is evident that CIS is a unifying concept that can be applied to all and any epithelium. Colonic adenoma is not the only misnomer for CIS. In fact, CIS of different epithelial origin is often given different names. For example, bronchioalveolar carcinoma of the lung, [4] borderline epithelial neoplasm of the ovary, noninvasive urothelial carcinoma of the urinary tract, high-grade squamous intraepithelial lesion of the cervix, complex hyperplasia of the endometrium, prostate intraepithelial neoplasia, etc., are all CIS in nature. However, each one of these is a subject in itself and requires a separate essay to deal with.