The term indicating that the tumor has undergone malignant changes but is still limited to the site where it originated is?

The term that denotes a tumor which has undergone malignant changes but remains confined to its original site is "Carcinoma in situ." This term specifically refers to a group of abnormal cells that are found in the place where they first formed and have not spread to nearby tissues. Knowing this helps to understand the behavior of the tumor before it might progress to invasive cancer, where cancer cells would invade surrounding tissues and potentially spread to other parts of the body.

In this context, identifying the cancerous nature while still being localized is crucial for treatment and prognosis. It often indicates a better outcome compared to more advanced stages of cancer. Understanding this distinction is vital for medical coding, as it helps accurately assign appropriate codes for medical records and billing.