What is the difference between carcinoma in situ and invasive carcinoma?

The differences between invasive cancer and carcinoma in situ include variations in the extent of cell spread, tissue invasiveness, metastatic potential, treatment approaches, and prognosis. The specific analysis is as follows:

1. Extent of cell spread: Invasive cancer refers to cancer cells that have spread to surrounding tissues or other organs, forming metastatic lesions. In contrast, carcinoma in situ refers to cancer cells confined strictly to their original site, without spreading to surrounding tissues or other organs.

2. Tissue invasiveness: Invasive cancer is characterized by its ability to infiltrate—cancer cells can penetrate the basement membrane and invade surrounding tissues, disrupting normal tissue architecture. In carcinoma in situ, cancer cells remain confined within the epithelial layer, have not penetrated the basement membrane, and do not invade surrounding tissues.

3. Metastatic potential: Invasive cancer has the potential to metastasize; cancer cells can enter distant sites via the bloodstream or lymphatic system, leading to distant metastases. Carcinoma in situ lacks this metastatic capability and does not spread to other areas.

4. Treatment approaches: Because invasive cancer has already spread to surrounding tissues or other organs, it is more difficult to treat and typically requires comprehensive treatments such as surgical resection, radiotherapy, and chemotherapy. In contrast, carcinoma in situ can often be effectively managed with local treatments such as surgical excision or laser therapy.

5. Prognosis: The prognosis for invasive cancer is relatively poor due to its spread to other areas, greater treatment difficulty, and higher risks of recurrence and metastasis. In contrast, the prognosis for carcinoma in situ is generally favorable, as it is limited to the primary site; timely treatment can effectively control the disease and prevent progression or metastasis.

It should be noted that although carcinoma in situ has not spread to surrounding tissues or other organs, if left untreated, it may progress into invasive cancer. Therefore, detected cases of carcinoma in situ still require active treatment and regular follow-up.