What Is the Best Surgical Margin for a Basal Cell Carcinoma?
Basal cell carcinoma (BCCA) is the most common skin cancer that I treat. In the United States, the annual incidence rate of BCCA is 146 for every 100,00 people. BCCA is usually an indolent, locally invasive neoplasm that can occur at any age. However, the incidence of BCCA increases significantly after 40 years of age. The treatment of choice for basal cell carcinoma is surgical excision which can be accomplished in a variety of fashions: curettage (where no margins are identified), surgical excision with pre-determined margins of clinically normal tissue, excision under frozen section control (where a pathologist examines the tumor immediately after excision and prior to closure), or Moh’s micrographic surgery. The reason that I, as a plastic surgeon, see so many of these patients is that about 85% of these tumors occur in the cosmetically-sensitive head and neck area of the body. Whether these tumors are excised by my patient’s dermatologist using Moh’s technique, or by myself, the defects can be very disfiguring and virtually always require some sort of reconstructive procedure. That is where the reconstructive surgeon comes in.
There are many studies in the plastic surgery and dermatology literature that address the proper size of a surgical margin (i.e. the amount, in millimeters, of normal tissue surrounding the tumor) that should routinely be removed. A recent study (Plast. Reconstr. Surg Vol 126, No. 4 Oct, 2010. p 1222) compared all of the data from 37 of the most relevant, recent studies in order to determine three things:
1) What is a reasonable treatment goal for a patient with a small, well-demarcated basal cell carcinoma lesion up to 2 cm diameter?
2) What are appropriate surgical margins that will provide that treatment objective to the patient?
3) What is the appropriate management of the patient with a positive pathologic margin that is determined after reconstruction has already been completed?
TREATMENT GOAL: Reported cure rates for BCCA range from 90-100%. This study found that a goal of 5 percent or less recurrence over a 2-5 year time span is considered reasonable for surgical management of BCCA (non-morpheaform types only).*
OPTIMAL SURGICAL MARGINS: The goal of treatment with these tumors is to safely predict appropriate margins of resection of BCCA lesions while sacrificing a minimum amount of healthy surrounding skin. In this study, they compared margins from 1 to 4mm, with margins of 5mm (without having to utilize frozen section analysis by a pathologist). They found that for surgeons who desire at least a 95% cure rate, that a 3mm surgical margin can be safely used for BCCA 2 cm or smaller in greatest diameter.
POSTOPERATIVE MANAGEMENT OF A POSITIVE PATHOLOGIC MARGIN: Recurrence rates for lesions with positive pathologic margins that were treated with observation alone (i.e. patients did not go back for repeat excision) were an average of 27%. This is indeed high. This suggests that observation alone in all patients with this scenario is not advisable, since the risk of recurrence to very high. The study suggests that a case-by-case evaluation be done in this situation that addresses the risk of observation/surveillance with the morbidity/risk of re-resection.
*In reality, the 2-5 year recurrence rate for BCCA is probably much lower than 5 percent. Although I would like to achieve a zero percent recurrence rate for my patients, that number is very unrealistic. The important thing to know is that these tumors are frequently only locally aggressive, and rarely metastasize (with rare exception).