Curettage and Electrodesiccation

Introduction

Curettage and electrodesiccation (CE) is a technique available to dermatologists to destroy benign entities and non-melanoma skin cancer (NMSC). The use of CE for the treatment of NMSC has been both praised and criticized, revealing its advantages and limitations. In order to appropriately employ CE to treat NMSC, it is essential to learn the basis for selecting CE, the proper technique, the likely cure rates for given lesions, and the expected cosmetic result, in order to provide patients with the best outcome.

Formerly the dermatologists' treatment of choice for many skin cancers, CE is now only one method in an increasing therapeutic armamentarium. To utilize CE most judiciously, it is valuable to examine this technique in depth and to come to some thoughtful conclusions about its use for patients with skin cancer.

History

Electrodesiccation of skin lesion was first established in 1911 by William Clark, who noted superficial tissue drying (desiccation) when he applied a high voltage, low current to the skin, through a monoterminal electrode. Clark reported the treatment of a variety of skin lesions, including some basal cell carcinomas, with electrodesiccation alone. The technique of electrodesiccation became available to the office practitioner through the development of instrumentation such as the original Hyfrecator units produced by the Birtcher Corporation.

The literature surrounding the original implementation of curettage is quite sparse. Use of the dermal curette was first reported in 1870 by Dr. Henry Piffard. Several years later, Dr. Edward Wigglesworth used the dermal curette to treat a variety of skin lesions, including psoriasis and syphilitic condylomata. In 1902, Dr. George Fox introduced the Fox model curette, which remains the most popular curette today. As dermatology evolved in the 1950s and 1960s, an increasing number of epithelial tumors were primarily treated by CE or by curettage alone. At this time, many dermatologists received little training in surgery and most large lesions were handled either through excision by general surgeons or plastic surgeons, or by radiation therapy. As dermatologists explored avenues for office-based treatment of cutaneous tumors, the technique of CE was embraced as an efficient method for the removal of benign lesions and NMSC.

Description of procedure/therapy

Electrosurgery principles

The use of electrosurgery requires understanding the principles of electricity and waveforms. The five principles of electricity are current, resistance, voltage, work, and power ( Table 41.1 ). These principles determine the functionality of an electrosurgery unit. Waveform refers to the shape of an electromagnetic field generated from a high-frequency alternating current. The waveform factors to consider are whether it is damped or undamped and whether it is continuous or discontinuous ( Fig. 41.1 ).

Table 41.1

Electricity Principles

Principle	Definition	Units	Pearls/Application
Current	Flows of electrons through a conductor per second Density = current/conductor cross-sectional area	Amperes	The thinner the electrosurgical tip, the greater the current density, resulting in greater tissue destruction
Direct	Electron flow is in one direction		Used in iontophoresis and electrolysis
Alternating	Electron flow is constantly alternating direction; with high frequencies there is no cellular depolarization resulting in the generation of heat		Frequencies of 500–2000 Hz generate heat with no/minimal neuromuscular depolarization
Resistance	A conductor's ability to impede the passage of an electric current Directly proportional to the length of the substance Inversely proportional to the cross-sectional area	Ohms	Muscle: low resistance Fat: high resistance Skin: high when dry, low when wet
Voltage	Electrical force that induces electron flow Current flows from high to low electron concentration Volts = current × resistance	Volts	Little heat is created with low resistance
Work	Current flow over a distance due to voltage difference Work = force × distance	Joules	Tissue resistance to current results in heat generation
Power	Rate of heat generated due to tissue resistance to the passage of current created by a voltage potential Power = current × voltage	Watts (joules/s)	Power increases are greater with increased current rather than voltage

Combining the five electricity principles and the type of waveform, in addition to whether the electrosurgery unit is monoterminal (no grounding pad used, the current is randomly dispersed to the environment) or biterminal (grounding pad used, the current flows from one electrode to the other), determines the type of destruction that the electrosurgery unit creates in the tissue ( Fig. 41.2 ). Electrodesiccation is typically performed using a monoterminal unit with high voltage, low amperage, and a discontinuous and damped waveform. The procedure invokes a superficial level of destruction with minimal damage to the deeper structures. It is performed by gliding the electrodesiccator tip gently along the surface of the tissue until a thin char is achieved.