When it comes to cancer staging, people often hear about stages 1, 2, 3, and 4 of cancer. However, there is actually stage zero cancer that, as you might guess, comes before stage 1. Stage zero cancer is also known as carcinoma in situ. Carcinoma in situ cells are limited to the location where they first formed, such as within the epithelial layer of the mucosa or the epidermis of the skin, and have not spread to surrounding tissue.
Theoretically, most cancers develop from carcinoma in situ, but not all cancers can be detected at the earliest stages. Carcinoma in situ is relatively common in the diagnosis of the following cancers.
Stage Zero Breast Cancer: Accounts for 1 in 5 Cases
Ductal carcinoma in situ (DCIS) is a type of breast cancer. Its cancerous cells originate from the ductal epithelial cells of the milk ducts. This cancer is also known as noninvasive breast cancer or precancerous lesions of the breast, and usually does not metastasize and spread.Most patients with ductal carcinoma in situ do not experience any symptoms, and only a small number of patients notice breast lumps, itchy skin, or bloody nipple discharge. In most patients, ductal carcinoma in situ is first detected during breast cancer mammography screening and confirmed by needle biopsy.
The cancerous lump in ductal carcinoma in situ can be large or small, and multiple lumps can appear at the same time. Surgical removal of the lump is the most common treatment for ductal carcinoma in situ.
According to the Cleveland Clinic, because DCIS is contained within a specific area of the breast and hasn’t spread, the disease can be controlled and cured with appropriate treatment. After treatment, outcomes are usually excellent.
As breast cancer screening has become more common, the detection rate of ductal carcinoma in situ has also increased significantly. Ductal carcinoma in situ accounts for more than 20 percent of newly diagnosed breast cancers each year, raising concerns among medical experts that this type of carcinoma in situ is being “overdiagnosed.” However, some surgeons believe that early diagnosis and early treatment are always good for patients.
Another type of carcinoma in situ in the breast is called lobular carcinoma in situ (LCIS). It is relatively uncommon and has not yet been classified as breast cancer, but patients have an increased risk of developing breast cancer in the future. The main approaches to
treatment for LCIS include observation, medication to prevent breast cancer, and surgical resection.
Stage Zero Bladder Cancer: High-Risk Tumors
Bladder cancer is more common in older men. In some patients with bladder cancer, the tumor is limited to the cell layer of the bladder mucosa epithelium at the beginning of diagnosis. It is called
carcinoma in situ of the bladder,
or a flat carcinoma.
The most common symptom of bladder carcinoma in situ is blood in the urine (hematuria). Patients with this symptom should seek medical attention as soon as possible.
In addition to analyzing the urine sediments, the examination for bladder carcinoma in situ requires a small biopsy of tissue under the guidance of a cystoscope. However, bladder carcinoma in situ is easily confused with bladder inflammation under ordinary cystoscopes, so doctors usually need to use higher-end fluorescent cystoscopes or narrow-band imaging cystoscopes to improve the detection rate of bladder carcinoma in situ.
It is worth noting that there are many
high-grade tumors in bladder carcinoma in situ—that is, tumor cells that are highly malignant and can easily spread to the muscle layer of the bladder. Therefore, the treatment of bladder carcinoma in situ is very important, and treatment methods include surgery, immunotherapy, chemotherapy, and laser therapy.
Stage Zero Lung Cancer: 100 Percent 5-Year Recurrence-Free Rate After Surgery
Lung cancer is the second most common cancer in the world. More than 2 million patients are diagnosed with lung cancer every year, of which
nearly 40 percent are adenocarcinoma, and
less than 4 percent are adenocarcinoma in situ of the lung (formerly called bronchioloalveolar carcinoma).
Although smoking is the number one risk factor for lung cancer, adenocarcinoma in situ of the lung often develops in people who have never smoked. The tumor (nodule) of adenocarcinoma in situ of the lung is less than 30 millimeters in diameter, grows very slowly, and rarely metastasizes (
pdf).
The main treatment for adenocarcinoma in situ of the lung is surgical resection of the mass, which has a
100 percent five-year recurrence-free rate after surgery. Some doctors and patients prefer conservative observation and regular follow-up to check the tumor growth of adenocarcinoma in situ. In such cases, considering the risk of lung cancer induced by CT radiation, the time interval between examinations is generally prolonged.
It is worth mentioning that in the
new classification criteria for lung tumors announced by the World Health Organization in 2021, lung adenocarcinoma in situ was separated from the classification of lung adenocarcinoma, and included in the category of precursor glandular lesions of lung cancer. However, the name of adenocarcinoma in situ remains unchanged.
Stage Zero Cervical Cancer: Avoid HPV Infection to Prevent
The most common cervical carcinoma in situ, also known as 3rd-grade cervical intraepithelial neoplasia (CIN3), is squamous cell carcinoma in situ of the cervix, in which the mutated cells spread throughout the epithelium of the cervix but have not spread beyond the epithelial layer.
Similar to the common cervical cancer, squamous cell carcinoma in situ of the cervix is mainly caused by the sexually transmitted virus HPV. It is almost impossible to develop squamous cell carcinoma in situ of the cervix without an HPV infection. Therefore, avoiding getting HPV is the
key to this cancer’s prevention.
Squamous cell carcinoma in situ of the cervix does not cause symptoms, but abnormal cells can be found in routine Pap smears and further diagnosed by colposcopy.
Patients diagnosed with squamous cell carcinoma in situ of the cervix should be actively treated to avoid further progression of the disease. Common treatments include loop electrosurgical excision procedure, conization, and hysterectomy.
Stage Zero Skin Cancer: Requires Timely Treatment
There are three major types of skin cancer: squamous cell carcinoma, basal cell carcinoma, and melanoma, all of which can be diagnosed at stage zero (carcinoma in situ).Squamous cell carcinoma in situ of the skin,
also known as Bowen’s disease, is considered an early-stage squamous cell skin cancer. Bowen’s disease is associated with ultraviolet-light exposure. The lesions appear on sun-exposed parts of the skin as eczema-like reddish-brown patches that are scaly or crusted, sometimes resembling psoriasis.
Left untreated, Bowen’s disease patches may spread deeper and eventually develop into skin cancer. Bowen’s disease can be treated with electrodesiccation, curettage with cautery, or surgical excision; doctors may also destroy the tumor using methods such as cryotherapy and topical chemotherapy drugs on the skin.
Basal cell carcinoma is more common in fair-skinned people and appears as shiny and pearly skin bumps. It usually does not metastasize, so the detection rate of carcinoma in situ is higher. In fact,
clinicians rarely need to determine the stage of basal cell carcinomas, as they are mostly caught early and cured.
Melanoma is the skin cancer that is most likely to spread and metastasize, but there are also many diagnoses of carcinoma in situ. An estimated
186,680 cases of melanoma will be diagnosed in the United States in 2023. Of those, 89,070 cases will be in situ (noninvasive), confined to the epidermis (the top layer of skin), and 97,610 cases will be invasive, penetrating the epidermis into the skin’s second layer (the dermis). Surgical excision is the main treatment for melanoma in situ, but the surgical margin of the excision should be
appropriately expanded to ensure effective prevention of recurrence.
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