Question: Connecticut Subscriber Answer: The term "carcinoma in situ" refers to tumor cells undergoing malignant changes but not invading the surrounding tissue. Your oncologist may also refer to these as intraepithelial, noninvasive, or preinvasive carcinoma, but ask the physician to specify "in situ" when that is the appropriate diagnosis. Other conditions may be non-infiltrating, and you don't want to make an assumption that leads to reporting the wrong diagnosis.