Carcinoma in situ (CIS)

Carcinoma in situ (CIS) is an early-stage, non-invasive form of cancer in which abnormal cells are confined to the epithelium – the thin layer of tissue that lines the surfaces and internal structures of the body. “In situ” means “in its original place,” indicating that the cancerous cells have not spread into surrounding tissues or beyond their initial location. Carcinoma in situ represents the earliest form of cancer, often described as stage 0. If left untreated, the abnormal cells can spread beyond the epithelium in a process called invasion.

What causes carcinoma in situ?

The specific cause of carcinoma in situ depends on the type of tumour and where it occurs in the body. Generally, carcinoma in situ arises from genetic changes or mutations in epithelial cells.

Here are some examples related to specific locations:

• Breast: Hormonal factors, age, family history, and genetic mutations (such as BRCA gene mutations) are known risk factors.
• Skin: Chronic exposure to ultraviolet (UV) light from the sun or tanning beds increases the risk.
• Cervix: Infection with certain high-risk types of human papillomavirus (HPV) is a major factor.

Having risk factors doesn’t mean someone will definitely develop carcinoma in situ, and this disease can sometimes occur without apparent risk factors.

How serious is carcinoma in situ?

Carcinoma in situ is a noninvasive form of cancer, meaning that the abnormal cells have not spread beyond their original location. Although carcinoma in situ itself does not invade surrounding tissues, it has the potential to progress to invasive cancer if not treated. The risk of progression varies depending on the type and location of the tumor. Early detection and appropriate treatment are important to prevent progression and effectively manage the condition. Treatment often involves removing or destroying the abnormal cells, and regular follow-up is usually recommended.

Types of carcinoma in situ

Carcinoma in situ can occur in various parts of the body. Identifying the specific type of carcinoma in situ helps determine the most effective management and treatment approach.

Here are some common types:

Ductal carcinoma in situ (DCIS)

DCIS is a non-invasive breast cancer confined to the lining of the milk ducts. It is usually detected through mammography and can progress to invasive breast cancer if left untreated.

Lobular carcinoma in situ (LCIS)

LCIS involves abnormal cells in the breast lobules—the glands that produce milk. Although LCIS itself isn’t considered cancer, it indicates an increased risk of invasive breast cancer developing in the future.

Cervical intraepithelial neoplasia (CIN)

CIN refers to abnormal cells on the surface of the cervix, often detected through Pap tests. Without treatment, CIN can progress to invasive cervical cancer.

Squamous cell carcinoma in situ

This type of carcinoma in situ commonly affects the skin, presenting as red, scaly patches. However, it can also occur in any other part of the body lined by squamous cells, including the mouth, throat, and genital regions. Bowen’s disease has the potential to develop into invasive squamous cell carcinoma if untreated.

Urothelial carcinoma in situ

This CIS type affects the urinary tract lining, most commonly the bladder. It carries a high risk of progressing to invasive bladder cancer if not addressed promptly.

Adenocarcinoma in situ

Adenocarcinoma in situ involves glandular cells and can develop in organs such as the lungs, cervix, and colon. It is considered an early stage that can progress to invasive adenocarcinoma.

About this article

Doctors wrote this article to assist you in reading and comprehending your pathology report. Feel free to reach out to us with any questions about this article or your pathology report. To get a comprehensive introduction to your pathology report, read this article.