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Cone biopsy: perfecting the procedure

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When colposcopy and cervical biopsy are inadequate in evaluating cervical dysplasia, cone biopsy of the cervix often will be both diagnostic and therapeutic.


 

References

Key points
  • Cone biopsy typically includes the removal of the entire squamocolumnar junction of the cervix, generally agreed to be the site of origin of squamous cell carcinoma.
  • Inject a premixed solution of 2% xylocaine and epinephrine in a concentration of 1:200,000 into the cervical stroma at 12 o’clock outside the intended margin.
  • For a “cold-knife” cone, use a #11 surgical blade to begin a circular incision starting at 12 o’clock on the face of the cervix.

Cone biopsy of the cervix has been used for more than a century to rule out the presence of invasive carcinoma in women with squamous intraepithelial lesions (SIL). And while less invasive techniques such as colposcopy and loop electrosurgical excision procedures (LEEP) have reduced the need for diagnostic conization dramatically, cervical cone biopsy becomes necessary when these techniques prove inadequate.

Indications

When routine screening reveals abnormal cervical cytology such as atypical squamous cells of undetermined significance (ASCUS), low-grade squamous intraepithelial lesions (LGSIL), and high-grade squamous intraepithelial lesions (HGSIL), colposcopy and directed biopsy often are indicated. They help the physician rule out the presence of invasive carcinoma and determine the grade and distribution of the intraepithelial lesion. Currently, only HGSIL is considered premalignant and requires aggressive treatment via cone biopsy.1 Additional indications for the procedure are listed in Table 1.

Remove a single specimen that includes the entire transformation zone.

From a diagnostic standpoint, cone biopsy should be performed when the endocervical curettage is positive for dysplasia because it is difficult to grade the severity of dysplasia on the basis of the scant tissue fragments obtained by curettage. From a therapeutic standpoint, lesions that involve the endocervical canal are less likely to be adequately treated by destructive techniques such as cryotherapy. Thus, for most women, cone biopsy of the cervix is both diagnostic and therapeutic.

TABLE 1

Indications for cervical conization

  • When the clinician is unable to perform a satisfactory colposcopy and cervical cytology demonstrates HGSIL
  • When SIL is present in the endocervical curettage sample
  • When squamous cell carcinoma in situ or microinvasive carci-noma is diagnosed or suspected by cytology, colposcopy, or directed biopsy
  • When cervical cytology suggests a higher-grade lesion than that found by colposcopic-directed biopsy
  • When cytology, biopsy, or endocervical curettage suggest the presence of an endocervical glandular lesion.

Preparing for cone biopsy

Cone biopsy involves the surgical excision of a wedge-shaped portion of the ecto- and endocervix, including the removal of the entire squamocolumnar junction (SC junction) of the cervix, generally agreed to be the site of origin of squamous cell carcinoma of the cervix. The procedure may be performed using a scalpel, electroexcision (LEEP or fine-needle electrode), or CO2 laser. The choice between performing “cold-knife” versus “hot-knife” conization is largely one of personal preference and depends on surgical experience, the size/severity of the lesion, and the desires of the patient. In most cases, I prefer to use electrocautery because of its technical simplicity and the ability to operate with only a local anesthetic. It is particularly appropriate for patients with an obvious ectocervical lesion and in young, nulliparous women in whom I am trying to minimize the amount of healthy cervical tissue removed.

The use of colposcopy, either preoperatively or intraoperatively, allows precise evaluation of the amount of cervical tissue needed to be removed and reduces the incidence of positive margins. The geometry, i.e., width and depth, of the cone specimen will vary from patient to patient, depending on the size and location of the dysplastic lesion, as well as the location of the SC junction. Specifically, the width of the cone (ectocervical portion) is determined by the size of the transformation zone and size and location of any ectocervical lesions. The depth of the cone (endocervical portion) is determined by the location of the SC junction, the presence or absence of endocervi-cal disease, or the suspicion of a glandular lesion. When a discrete intraepithelial lesion has not been identified, it is critical to rule out a significant endocervical lesion. Therefore, the amount of tissue I plan to remove is based on the following 2 factors:

  • Location of the SC junction. The more endocervical the SC junction is, the more likely the presence of a lesion higher in the canal. However, squamous intraepithelial lesions rarely extend higher than 2 cm into the canal.2
  • Endocervical gland involvement. SIL frequently involves the endocervical glands, often to a depth of 5 mm or less. Several investigators have suggested that excision of endocervical glands to a depth of 7 to 10 mm produces acceptable cure rates.3

Based on these 2 principles, the endocer-vical portion of the cone should be 20 mm wide (10 mm on either side of the canal) and no more than 2 cm deep.