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.

Korpan N: Atlas of cryosurgery, Wien, Springer, 2001.

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

Figure 52-1. A handheld cryotherapy unit is being used to spray actinic keratoses with liquid nitrogen. Note the cutaneous ice ball that forms in the treated areas.

Jackson A, Colver G, Dawber R: Cutaneous cryosurgery: principles and clinical practice, ed 3, New York, 2005, Taylor & Francis.

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

Acne

Acrochordon (skin tag)

Actinic cheilitis

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