# Cryosurgery and Electrosurgery in Dermatology

## Introduction

Cryosurgery and electrosurgery are two of the most widely used destructive modalities in dermatologic practice. Mastery of their principles, techniques, and appropriate indications enables efficient treatment of a broad range of benign and malignant cutaneous lesions.

## Cryosurgery

### Mechanism of Tissue Destruction

Cryosurgery destroys tissue through several complementary mechanisms. **Rapid freezing** causes intracellular ice crystal formation, leading to direct mechanical disruption of cell membranes. **Slow thaw** allows ice crystal recrystallization and osmotic injury as extracellular ice melts before intracellular ice. **Vascular stasis** occurs as endothelial damage leads to thrombosis and ischemic necrosis within 24 to 48 hours. **Immunologic effects** from the release of intracellular antigens may trigger an anti-tumor immune response. Tissue destruction occurs at temperatures of **-25 to -50 degrees C** for malignant cells, while benign lesions are destroyed at -20 to -25 degrees C.

### Cryogens

**Liquid nitrogen (LN2)** has a boiling point of -196 degrees C and is the most commonly used cryogen, delivered via spray, probe, or cotton-tipped applicator. **Nitrous oxide** has a boiling point of -89 degrees C and is used in closed-probe cryosurgical units. **Dimethyl ether/propane (DMEP)** is available as over-the-counter products with a boiling point of -24 degrees C, which is insufficient for treating malignant lesions.

### Techniques

The **spray technique** uses an open spray from a handheld Cry-Ac unit, allowing treatment of irregular surfaces and offering the most versatility. The **probe technique** applies a cryoprobe directly to the lesion and is useful for well-circumscribed lesions and eyelid tumors. The **cotton-tipped applicator** dipped in LN2 and applied to the lesion is the least controlled method, suitable only for small benign lesions. For malignant lesions, a **double freeze-thaw cycle** is the standard approach.

<image>Diagram showing three cryosurgery delivery methods (open spray, cryoprobe, cotton-tip applicator) with cross-sectional view of ice ball formation in tissue showing lateral spread approximately equal to depth of freeze</image>

### Monitoring the Freeze

A **thermocouple needle** measures tissue temperature at the deep margin, with a target of -50 degrees C for malignancies. The **lateral spread of freeze (LSF)** indicates that the ice ball extends laterally approximately equal to its depth, so a 5 mm LSF corresponds to roughly 5 mm depth of freeze. **Freeze time** is typically 15 to 30 seconds for benign lesions and 30 to 60 seconds for premalignant or malignant lesions.

### Indications

For **benign** lesions, cryosurgery treats actinic keratoses, viral warts, seborrheic keratoses, molluscum contagiosum, dermatofibromas, and keloids (intralesional). For **premalignant and malignant** lesions, it can be used for actinic keratoses (field treatment), superficial BCC (selected cases), Bowen disease, and Kaposi sarcoma. Cryosurgery is **not recommended** for morpheaform BCC, invasive SCC, melanoma, or recurrent tumors.

### Complications

Expected effects include pain, erythema, edema, blister formation, and serosanguinous drainage. **Hypopigmentation** is a significant concern because melanocytes are more sensitive to cold injury than keratinocytes, necessitating caution in **skin of color**. **Alopecia** is permanent if the hair follicle bulge region is destroyed. **Nerve damage** may cause tingling or numbness if superficial nerves are in the freeze zone, though this is usually temporary. **Cartilage necrosis** is a risk on the ear and nasal tip with aggressive freezing. **Tendon damage** should prompt avoidance of aggressive cryosurgery over superficial tendons on the dorsal fingers.

## Electrosurgery

### Terminology and Physics

**Electrosurgery** involves the passage of high-frequency alternating current (greater than 100 kHz) through tissue to produce thermal effects. **Electrocautery** uses a heated wire tip that transfers heat to tissue by direct contact, and current does NOT pass through the patient (this modality is rarely used now). The key distinction is that electrosurgery uses the patient as part of the circuit, while electrocautery does not.

### Electrosurgical Modalities

#### Electrodesiccation

Electrodesiccation uses **monoterminal** (single electrode, no grounding pad) high-voltage, low-amperage current. It produces superficial tissue dehydration and charring, with current spreading laterally through tissue for **superficial destruction only**. It is used for seborrheic keratoses, skin tags, and small superficial BCCs (with curettage).

#### Electrofulguration

Electrofulguration is similar to electrodesiccation but the electrode is held **slightly away** from the tissue, causing current to arc (spark) to the tissue surface for even more superficial destruction. It is used for hemostasis of superficial bleeding and removal of filiform warts.

#### Electrocoagulation

Electrocoagulation is **biterminal** (requires a grounding pad), with current passing through tissue to the dispersive electrode. Higher amperage produces **deeper tissue coagulation and hemostasis** with greater depth of thermal destruction compared to electrodesiccation. It is used for hemostasis during excisional surgery and destruction of larger vascular lesions.

#### Electrosection (Cutting)

Electrosection uses continuous, undamped high-frequency current through a fine wire electrode, producing a **clean cutting action** with minimal lateral thermal damage. It is used for shave biopsies, shave excisions, and incisional procedures. **Blend mode** combines cutting and coagulation waveforms for simultaneous hemostasis.

<image>Comparison diagram of four electrosurgical modalities showing electrode configuration, waveform type (damped vs undamped), and depth of tissue effect for electrodesiccation, electrofulguration, electrocoagulation, and electrosection</image>

### Electrodesiccation and Curettage (ED&C)

ED&C is the **workhorse technique** for superficial non-melanoma skin cancers. The technique involves curetting the tumor (which has a softer texture than surrounding dermis), then electrodesiccating the base, and repeating for **3 cycles** (the traditional standard). **Cure rates** reach 95 to 97% for primary, well-defined, low-risk BCCs less than 1 cm. **Contraindications** include high-risk sites (central face, ears), aggressive BCC subtypes, recurrent tumors, and areas over hair-bearing scalp (poor wound healing, alopecia). The wound heals by **secondary intention** and produces a hypopigmented, atrophic scar. Importantly, ED&C does not allow histologic margin assessment.

### Safety Considerations

For **pacemakers and ICDs**, modern bipolar devices are generally safe, but cardiology should be consulted. Monopolar use should be avoided over the device, and a magnet should be available for ICD. **Grounding pad placement** should be on a well-vascularized, large muscle mass (thigh) close to the surgical site, avoiding bony prominences and scar tissue. **Surgical plume** contains viable viral DNA (HPV), chemical irritants, and carcinogens, making **smoke evacuation** devices essential. **Flammable hazards** require avoiding electrosurgery near oxygen, alcohol-based prep solutions (which must be allowed to fully dry), and drape materials. **Implanted metals** are generally safe with modern high-frequency devices, though prolonged activation directly over hardware should be avoided.

<image>Clinical photograph showing the electrodesiccation and curettage technique for superficial BCC: sequential images of curettage removing soft tumor tissue, electrodesiccation of the base, and the wound after three cycles</image>

## Comparing Cryosurgery and Electrosurgery

| Feature | Cryosurgery | Electrosurgery (ED&C) |
|---------|-------------|----------------------|
| Tissue for histology | No | Curettings can be submitted |
| Hypopigmentation risk | High | Moderate |
| Depth control | Moderate (thermocouple) | Moderate (tactile feedback) |
| Wound healing | Eschar, secondary intention | Secondary intention |
| Use in pacemaker patients | Safe | Precautions needed |

## Key Clinical Pearls

Cryosurgery causes melanocyte destruction at temperatures warmer than those needed to kill keratinocytes, so caution must be exercised in darker skin types where hypopigmentation can be disfiguring. The double freeze-thaw cycle is essential for treating malignant or premalignant lesions with cryosurgery. ED&C relies on the textural difference between tumor and normal dermis, making it inappropriate for aggressive or sclerotic BCC subtypes where this distinction is lost. Smoke evacuation should always be used during electrosurgery because surgical plume contains viable HPV DNA and carcinogens. For pacemaker patients, cardiology consultation is recommended, and bipolar electrosurgery is preferred over monopolar when possible.

## References

1. Kuflik EG. Cryosurgery for skin cancer: 30-year experience and cure rates. *Dermatol Surg*. 2004;30(2 Pt 2):297-300.
2. Holt PJ. Cryotherapy for skin cancer: results over a 5-year period using liquid nitrogen spray cryosurgery. *Br J Dermatol*. 1988;119(2):231-240.
3. Tromovitch TA, Stegeman SJ. Electrodesiccation and curettage. In: Robinson JK, et al., eds. *Surgery of the Skin*. 3rd ed. Elsevier; 2015.
4. Gloster HM, Roenigk RK. Risk of acquiring human papillomavirus from the plume produced by the carbon dioxide laser in the treatment of warts. *J Am Acad Dermatol*. 1995;32(3):436-441.