- Ductal carcinoma in situ (DCIS):
- Is a noninvasive carcinoma of the breast
- It is defined as the proliferation of malignant epithelial cells:
- Confined to the mammary ducts and without evidence of invasion through the basement membrane
- Because it is noninvasive:
- DCIS does not pose a risk of metastasis
- Lobular carcinoma in situ (LCIS):
- Was previously considered a form of noninvasive carcinoma:
- But is now understood to be a benign entity that is a pathologic marker of increased breast cancer risk:
- In either breast
- But is now understood to be a benign entity that is a pathologic marker of increased breast cancer risk:
- Atypical lobular hyperplasia (ALH) and LCIS:
- Are both forms of lobular neoplasia and, together with atypical ductal hyperplasia (ADH):
- Represent proliferative nonmalignant breast lesions
- Are both forms of lobular neoplasia and, together with atypical ductal hyperplasia (ADH):
- Was previously considered a form of noninvasive carcinoma:















