Chapter 52 Cryosurgery
1. What is cryosurgery?
Cryosurgery is the controlled application of cold to cause tissue damage. It can be used to treat both benign and malignant skin conditions. With cryosurgery, the degree of tissue damage is controlled in order to destroy the target lesion with minimal damage to normal surrounding tissue.
Gage AA: History of cryosurgery, Semin Surg Oncol 14:99–109, 1998.
2. How does cryosurgery cause injury?
Freezing causes intracellular and extracellular ice crystals to form, and the subsequent vascular stasis causes tissue anoxia and necrosis. The most efficient technique employs a rapid freeze and slow thawing. Multiple short freezes produce more damage than a long freeze. Different cell types have variable susceptibility to the effects of freezing, with melanocytes being damaged at a much higher temperature than keratinocytes (−5° C versus −50° C). This differential freezing has implications for the treatment of melanocytic lesions, as well as the use of cryosurgery in patients with darkly pigmented skin.
Gage AA, Baust J: Mechanisms of tissue injury in cryosurgery, Cryobiology 37:171–186, 1998.
3. Which agents are used for cryosurgery?
Most cryosurgeons use liquid nitrogen. It is readily available, inexpensive, easy to store, easy to use, and it works quickly. Less commonly used cryogens are Freon 12, Freon 22, solid CO2, liquid N2O (nitrous oxide), and liquid helium (Table 52-1). Because a colder cryogen causes deeper destruction, the Freons, solid CO2, and nitrous oxide are used only for topical anesthesia and superficial destruction. Liquid nitrogen is the only agent that is reliable for deeper destruction.
4. Do you need a lot of expensive equipment to use cryosurgery?
No. Compared to other surgical techniques, the amount of equipment needed is modest. First, you need a reservoir for the liquid nitrogen. This is normally a 20- to 30-liter thermos (Dewar flask). From here, the liquid nitrogen (LN2) is transferred to smaller containers. For basic cryosurgery, most dermatologists use small, handheld thermoses that spray the LN2 directly on the skin (Fig. 52-1). There are also various probes, neoprene cones, and thermocouple-pyrometer systems to treat malignant lesions.
Table 52-1. Cryogens Used in Cryosurgery
| CRYOGEN | BOILING POINT (°C) |
|---|---|
| Liquid nitrogen | −195.8 |
| Nitrous oxide, liquid | −89.5 |
| Carbon dioxide, solid | −8.5 |
| Chlorodifluoromethane (Freon 22) | −40.8 |
| Dichlorofluoromethane (Freon 12) | −27.8 |
5. What types of skin conditions can be treated with cryosurgery?
Both benign (Table 52-2) and malignant (Table 52-3) lesions can be treated by cryosurgery. The most common lesions are warts, actinic keratoses, seborrheic keratoses, and molluscum contagiosum. Cryosurgery is one of the most common procedures performed by dermatologists.
Table 52-2. Benign Lesions Treatable by Cryosurgery
Table 52-3. Malignant Lesions Requiring Monitoring During Cryosurgery
Andrews MD: Cryosurgery for common skin conditions, Am Fam Physician 69:2365–2372, 2004.
6. How is cryosurgery performed?
There are several ways to apply cryogens. Various sizes of swabs can be dipped in LN2 and touched to the lesion to freeze it. Due to the rapid dispersal of cold, swabs do not result in as much tissue cooling as the direct application of LN2 to the skin. Swabs are not used to treat malignancies. Various surgical instruments, such as hemostats and pick-ups (tweezers), can be used for cryosurgery of raised or pedunculated lesions. The surgical instrument is submerged in LN2 for 20 to 30 seconds and then the target lesion is grasped with the instrument. It is best to use a separate swab or surgical instrument and cup of cryogen for each patient to avoid cross-contamination
The spray technique uses modified thermoses that allow the LN2 to spray out of a nozzle (see Fig. 52-1). The degree of freezing is changed by the nozzle size, the pressure in the thermos, the distance to the lesion, and the length of freeze. This apparatus can be used for several hours, and contamination is not an issue. It also can treat very large lesions. A modification of this technique is to use neoprene cones to confine the LN2, causing a more concentrated freeze.
7. How are benign skin lesions treated?
The basic concept of all cryosurgery is that the depth of freezing is proportional to the width of the area frozen. When cryogen is applied, an ice ball forms in the skin for which the depth of freezing is equal to the radius of the surface freeze. Freezing 1 to 2 mm beyond the lesion with a single freeze-thaw cycle is adequate for most benign lesions. Warts can be deeper, so either a deeper freeze or multiple smaller freezes can be used. Thick seborrheic keratoses can be frozen lightly and quickly curetted. For benign lesions, you do not want to cause a scar, so it is always better to undertreat until you are experienced. When treating benign lesions, it is always important to be confident in your clinical diagnosis. If you have questions about whether or not a lesion is benign, or if a lesion does not resolve with cryosurgery, a biopsy should be performed to provide a histological diagnosis.
Jester DM: Office procedures: cryotherapy of dermal abnormalities, Prim Care 24:269–280, 1997.
8. How do you treat malignant lesions?
In treating cancers, we need to be very sure we treat them adequately. Most importantly, you should be able to clinically identify the margins of the lesion. Second, you must know the histology of the cancer to be sure cryosurgery is appropriate. Third, you must have equipment that ensures you reach a temperature of −50° C to −60° C beyond the peripheral extent and depth of the cancer. Malignant lesions require longer freeze times than benign lesions. Most malignant tumors require at least a 30-second freeze with two freeze-thaw cycles. Curetting or shaving tumors first to delineate and debulk the lesion prior to cryosurgery can permit more effective treatment. For large tumors, multiple treatments are often required. Repeat biopsies after cryosurgery can histologically confirm the resolution of the tumor.
Graham GF: Cryosurgery in the management of cutaneous malignancies, Clin Dermatol 19:321–327, 2001.
9. Is cryosurgery a preferred method for the treatment of cutaneous malignancy?
The treatment of cutaneous cancers by cryosurgery is not accepted by all dermatologists. In general, surgically oriented dermatologists feel that the demonstration of negative surgical margins is preferable to cryosurgery for significant cancers. In addition, cryosurgery can have significant postoperative morbidity for patients and may result in less than ideal scars. As a result, many dermatologists reserve cryosurgery for malignant lesions to special circumstances. In particular, patients who cannot tolerate conventional surgery, due to other health concerns, are often ideal patients for cryosurgery. Cryosurgeons argue that the cure rates achieved by cryosurgery are comparable to those of other surgical modalities, especially when the margins of the tumor can be identified. They advocate that cryosurgery should be considered equivalent to surgical excision in the treatment of malignant cutaneous tumors.
10. What are the cure rates of cryosurgery for malignant lesions?
Experienced cryosurgeons who treat many skin cancers report cure rates of 95% to 98% for primary basal cell carcinomas. These cure rates are comparable to those reported with surgery and radiation therapy. Similar rates are reported for the treatment of squamous cell carcinoma with cryosurgery. Lentigo maligna has also been successfully treated with cryosurgery due to its superficial nature and the sensitivity of melanocytes to freezing. Cure rates of great than 90% have been reported with cryosurgery in the treatment of lentigo maligna. However, cryosurgery is not an appropriate therapy for invasive melanoma. The cure rates using cryosurgery, radiation therapy, or excisional surgery for aggressive or recurrent skin cancers are significantly lower than those reported for simple, primary tumors. In these cases, Mohs micrographic surgery is often recommended.
11. Are there contraindications to cryosurgery?
People with cold-related conditions, such as cryoglobulinemia, cryofibrinogenemia, cold urticaria, and Raynaud’s disease, should not be treated with cryosurgery. Patients with heavily pigmented skin should be treated with caution because they are more likely to heal with hyperpigmented or hypopigmented scars, due to the sensitivity of melanocytes to freezing. In addition, the use of cryosurgery in hair-bearing areas may result in alopecia.
13. What are the complications of cryosurgery?
After using cryosurgery, the wound is allowed to heal by itself (second intention). A normal cryosurgery wound can blister, ooze, form an eschar, and take 1 to 6 weeks to heal. Complications are uncommon and include infection, hypertrophic scars, nerve damage, and unacceptable scars. Before performing cryosurgery, the normal course of healing and the potential risks of the procedure should be discussed with the patient.
