Cone biopsy

Giuseppe Del Priore

Introduction

The cone biopsy, the removal of a cone-shaped portion of the cervix, has been performed by gynecologists for decades. Recently, the electrosurgical technique referred to as the loop electrosurgical excision procedure' (LEEP) or 'loop excision of the transformation zone' (LETZ) has gained popularity. It has several advantages over other methods such as laser, cryotherapy and scalpel excision: these include less bleeding and discomfort, and the avoidance of general anesthesia, while still providing a reasonable specimen for pathologic interpretation. The scalpel and LEEP techniques are generally equivalent in their clinically significant outcomes, e.g. cure rates. However, the scalpel cone tends to be larger. This is not a particular advantage except perhaps when used in patients with adenocarcinoma of the endocervix: because this lesion may be more multifocal than squamous lesions, a larger specimen may be more likely to remove all of the lesion. As it may occasionally be necessary to perform a scalpel cone biopsy, all gynecologists should be familiar with both techniques. The histological specimen obtained by scalpel or LEEP allows assessment of excision margins. If cervical intraepithelial neoplasia (CIN) extends to the excision margins, the LEEP specimen is not reliably predictive of recurrence. Thus a scalpel cone biopsy is useful in cases of suspected microinvasion as well as in those cases of suspected adenocarcinoma.

Indications

Cone biopsy is indicated for the diagnosis or exclusion of microinvasive cervical cancer suspected from a presurgical Papanicolaou (Pap) smear or colposcopic punch biopsy. It should also be used to exclude and possibly treat endocervical adenocarcinoma. As mentioned above, a large scalpel cone biopsy may be a better option for these women. A LEEP cone biopsy is also indicated for patients with high-grade squamous epithelial lesions on Pap smear but no colposcopically identifiable lesion.

Anatomic considerations

Vascular supply

A small descending branch of the uterine artery supplies the cervix. This vessel can usually be found laterally in the vaginal portion of the cervix at the 3 o'clock and 9 o'clock positions.

Innervation

The nerves of the cervix arise from the hypogastric plexus. Specific branches from this plexus to the cervix, sometimes known as the uterovaginal plexus, are found in the broad ligament. More distally, the uterine cervical ganglion may be identified in the paracervical tissue closest to the cervix. The autonomic sympathetic nerves arise from the sympathetic trunk originating in the nerve roots from T10 to L1. The parasympathetic nerves arise from the roots of S2 to S4.

Muscles involved

The cervix sits above the urogenital diaphragm and thus has no direct muscle connection.

Bony landmarks

The cervix lies roughly in the plane of the ischial spine, being slightly anterior and inferior to it. It is important to consider the bony pelvic outlet when contemplating operating transvaginally on the cervix. For cone biopsies, only the most contracted pelvis would present a significant limitation.

Operative procedure

LEEP/LETZ

The procedure begins with the positioning of the patient's legs. The standard examination table with stirrups is usually suitable. A speculum large enough to hold the vaginal wall away from the cervix should be inserted. An insulated speculum is not necessary; in fact, if an insulated speculum has an undetected break in its insulation, it may allow a high-energy discharge and injure the patient. Regardless of the speculum used, a suction apparatus for evacuating the copious amount of smoke produced is essential. It may either be built into the speculum or clipped on to a standard one. Hand-held wall suction is generally not appropriate as the apparatus is usually too large to fit into the vagina.

Immediately before the actual procedure, colposcopy is used to identify the lesion. Local anesthetic solution should be administered circumferentially using a narrow gauge (27 G) reinforced needle such as a Potocky needle. Larger needles will lead to significantly more bleeding. Any local anesthetic solution with epinephrine (adrenaline) 1 in 100 000 may be used. Since water dissipates the electrosurgical current, excess stromal injections may make the procedure difficult, and shallow injection is advised. Discomfort from the local injection can be minimized by having the patient cough while the needle is placed on the surface of the cervix. The inferior movement of the cervix during this Valsalva maneuver is usually all that is needed to enable the needle to enter the cervix painlessly. The anesthetic solution should be administered early to allow enough time for it to take effect (Figure 1).

Different electrosurgical units have different settings and power sources. The only important parameter is current density. This is the actual energy that the cervix receives and is dependent on the diameter of the wire loop, the diameter of the wire itself, and the current setting. The highest current density possible should be used to minimize drag through the tissue and consequently cautery artifact. However, too high a current density will result in the loop wire breaking. If this should happen, completing the procedure will be more difficult because the operator will have to begin with a new wire loop in the middle of the specimen. Trial and error may be needed depending on the combination of generator and loop wires used.

Paracervical Clock

Figure 1

1 Reinforced shaft with thin needle

2 Squamocolumnar junction

3 Acetowhite epithelium

4 Speculum blades

After infiltration of the cervix, the operator should choose a loop size and shape that can remove the colposcopically identified acetowhite lesion with clear margins (Figure 2). It is customary to remove the entire transformation zone. The operator should practice the motion to be used before actually turning on the current. Once a comfortable motion has been established, the colposcope is used to identify the lesion and the transformation zone should be removed. A very low magnification setting is selected to facilitate ease of operability. Once everything has been checked, the operator applies the pure cutting current and smoothly passes the loop wire through the cervix, being careful not to touch the vaginal wall. The specimen may be grasped with forceps and removed for despatch to the pathology department. A sample of the endocervical canal may be obtained at this point using an endocervical curette or brush. It is also possible to use a smaller loop to obtain a 'top hat' of tissue if colposcopy suggests that the lesion is in the endocervical canal out of view.

Although there is usually no immediate bleeding, late rebleeding can be reduced by prophylactic cauterization of the cone base. This should be done using a ball or spatula tip cautery attachment. The current should be set on 'coagulation' at a sufficiently high current setting to exceed the capacitance of air.

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