<unk>  <unk>  is a group of abnormal cells. While they are a form of neoplasm, there is disagreement over whether<unk>  should be classified as cancer. This controversy also depends on the exact<unk>  in question (i.e. cervical, skin, breast). Some authors do not classify them as cancer, however, recognizing that they can potentially become cancer. Others classify certain types as a non-invasive form of cancer. The term "pre-cancer" has also been used. These abnormal cells grow in their normal place, thus "in situ" (from Latin for "in its place"). For example,<unk>  of the skin, also called Bowen's disease, is the accumulation of dysplastic epidermal cells within the epidermis only, that has failed to penetrate into the deeper dermis. For this reason,<unk>  will usually not form a tumor. Rather, the lesion is flat (in the skin, cervix, etc.) or follows the existing architecture of the organ (in the breast, lung, etc.). Exceptions include<unk>  of the colon (polyps), the bladder (preinvasive papillary cancer), or the breast (ductal<unk>  or lobular<unk> . Many forms of<unk>  have a high probability of progression into cancer, and therefore removal may be recommended; however, progression of<unk>  is known to be highly variable and not all<unk>  becomes invasive cancer. In the TNM classification,<unk>  is reported as<unk> N0M0 (stage 0).
Carcinoma in situ
Ductal carcinoma in situ
Acinic cell carcinoma
Epithelial dysplasia
Lobular carcinoma in situ
Field cancerization
Squamous intraepithelial lesion
Atypical adenomatous hyperplasia