Cryotherapy, often called cryosurgery or cryoablation, uses extreme cold to destroy abnormal tissue. This process involves applying a cryogen, typically liquid nitrogen, directly to the skin lesion to achieve a deep freeze. For skin cancer, this method is considered a local treatment, targeting a specific, localized area. Its application depends entirely on the type, size, and depth of the lesion being treated.
Understanding Cryotherapy
The mechanism by which cryotherapy eliminates abnormal cells relies on the destructive power of extreme cold. The most commonly used cryogen is liquid nitrogen, which has a boiling point of approximately -196°C (-321°F). This rapid temperature drop serves two main purposes in tissue destruction, which is known as necrosis.
The immediate effect of the cold is the rapid formation of ice crystals, first in the space outside the cells. This draws water out of the cells due to an osmotic gradient, concentrating the solutes inside. As the freezing continues, ice crystals form inside the cells, causing the cell membranes and internal structures to rupture, leading to direct cell death.
The subsequent thawing process also contributes significantly to tissue damage. As the ice crystals melt, the sudden shift in water concentration causes the cells to swell and burst. The extreme cold also damages the small blood vessels supplying the area, leading to vascular stasis. This cuts off the blood flow and oxygen supply, ensuring the destruction of the targeted tissue.
Which Skin Lesions Are Appropriate for Freezing
Cryotherapy is used to treat various skin conditions, including benign growths and specific types of skin cancer. It is widely used for precancerous lesions known as Actinic Keratoses (AKs). AKs are scaly patches of sun-damaged skin that can progress into cancer if left untreated.
For non-melanoma skin cancers, cryotherapy is an option, particularly for small, superficial, and low-risk lesions. The most common types treated are Basal Cell Carcinoma (BCC) and Squamous Cell Carcinoma (SCC) in situ. SCC in situ is an early form confined to the top layer of the skin. Success rates for these superficial cancers can be quite high when the lesions are small.
The application of this technique is highly determined by the lesion’s characteristics, including its size and location on the body. A key factor limiting its use is that the freezing process does not allow for a tissue sample to be examined by a pathologist to confirm clear margins afterward. For this reason, cryotherapy is generally not used for Melanoma, which is a far more aggressive form of skin cancer.
The Cryosurgery Procedure
The cryosurgery procedure is typically performed in an outpatient setting and involves minimal preparation. The healthcare provider applies the liquid nitrogen using one of three primary methods: a direct spray, a cotton-tipped applicator, or a cryoprobe. The choice of method depends on the size and depth of the abnormal tissue.
For malignant lesions, the goal is to freeze the tissue to a low target temperature, often around -50°C. The process relies on the freeze-thaw cycle. The tissue is frozen until an ice ball encompasses the lesion and a small margin of surrounding healthy tissue, held for a specified time, and then allowed to thaw completely. This cycle is typically repeated once or twice to maximize cell destruction.
Immediately following the procedure, the treated area will become red, swollen, and often form a blister. This blister, which may contain clear fluid or blood, is a sign that the tissue destruction was successful. Over the next several days to weeks, a scab will form over the site, and the dead tissue will slough off. Healing generally occurs within one to three weeks, depending on the body area.
When Cryotherapy is Not the Recommended Option
While cryotherapy is effective for select skin cancers, several factors make it unsuitable for higher-risk or more complex lesions. The inability to precisely control the depth of the freeze makes it a less desirable choice for lesions that are too large or extend deep into the skin. If the cancer is deep, the bottom layer of the tumor may not reach the necessary cytotoxic temperature, allowing cells to survive.
Anatomical location also plays a significant role in determining treatment suitability. Lesions near delicate structures, such as the eyes, nose, or nerves, may be better treated with a more controlled surgical method to avoid damage to surrounding healthy tissue. The procedure is also often avoided for cancers with aggressive or high-risk subtypes that have a greater potential for spread.
Cryotherapy is generally not the preferred option for recurrent skin cancers. Because the freezing destroys the tissue structure, it prevents the pathology analysis necessary to confirm complete removal, which is required for high-risk or recurrent tumors. In these situations, methods like Mohs surgery, which allows for immediate, complete margin assessment, are often chosen instead.