title: The efficacy of curettage in delineating margins of basal cell carcinoma before Mohs micrographic surgery.
abstract: BACKGROUND
  Curettage may be helpful as a preliminary step to outline the gross subclinical extensions of high-risk basal cell carcinomas (BCCs) before the first stage of Mohs micrographic surgery. Although many Mohs surgeons use curettage in the Mohs surgical setting, no prospective studies have as yet been performed that demonstrate the efficacy of curettage in delineating tumor margins before Mohs surgery.
  
  
  OBJECTIVE
  To document the efficacy of curettage in delineating BCC margins before Mohs micrographic surgery.
  
  
  METHODS
  This was a prospective evaluation of 599 patients with biopsy-proven BCCs treated with Mohs surgery. The preoperative dimensions of each tumor, the curetted dimensions before the first surgical stage, the proposed excisional margins before each surgical stage, and the final defect dimensions after each surgical stage were measured. The maximum curetted margin around each tumor was calculated and compared with typical Mohs excisional margins of 1, 2, 3, and 4 mm. A hypothetical 1-, 2-, 3-, or 4-mm excisional margin was added to the preoperative X and Y dimensions of each tumor, and the actual final defect sizes were compared with the hypothetical final defect sizes to determine whether an additional surgical stage would have been needed had curettage not been performed. The amount of tissue stretch occurring after specimen removal was calculated to determine whether tissue stretch falsely elevated the number of instances in which an additional surgical stage would have been needed had curettage not been performed.
  
  
  RESULTS
  The curetted margin around the observed extent of each tumor exceeded 1 mm in 87.6% of cases, 2 mm in 47.1% of cases, 3 mm in 19.7% of cases, and 4 mm in 5.7% of cases. The mean curetted margin was 1.7 mm. Taking a 1-mm margin in the first stage of Mohs surgery without first performing curettage would have necessitated an extra surgical stage in 99.2% of cases, whereas taking a 2-, 3-, or 4-mm margin would have necessitated an extra surgical stage in 93.0%, 88.1%, and 49.4% of cases, respectively. After calculating and eliminating the effects of tissue stretch, it was found that a 1-mm excisional margin taken in the first stage of Mohs surgery without first performing curettage would have necessitated an extra surgical stage in 99.0% of the cases. Taking a 2-, 3-, or 4-mm margin would have necessitated an extra surgical stage in 87.5%, 57.9%, and 29.5% of cases, respectively.
  
  
  CONCLUSIONS
  Careful debulking and palpation with the curette significantly reduce the number of Mohs surgical stages required for BCC clearance. Even after taking the effects of tissue stretch into consideration, a significant proportion of tumors would still require an additional stage for tumor clearance without aggressive presurgical curettage.
authors.affiliation: Department of Dermatology, College of Physicians and Surgeons of Columbia University, Columbia Presbyterian Medical Centrer, 161 Fort Washington Avenue, 12th Floor, New York, NY 10032, USA. dr221@columbia.edu
authors.forename: Désirée
authors.initials: D
authors.lastname: Ratner
authors.forename: Emilia
authors.initials: E
authors.lastname: Bagiella
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002280:Basal Cell Carcinoma / Q000473:pathology / Q000601:surgery*; D003475:Curettage / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015580:Mohs Surgery / Q000379:methods*; D009367:Neoplasm Staging; D011300:Preoperative Care / Q000379:methods*; D011446:Prospective Studies; D012878:Skin Neoplasms / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome