What meets the eye influences surgical margins

International report - Recent Mohs micrographic surgery (MMS) studies have shown that pigmented basal cell carcinomas (PBCC) require a smaller surgical margin for complete tumor excision, as compared to nonpigmented lesions, and that the early treatment of basal cell carcinoma (BCC) is associated with less subclinical microscopic invasion of tumor cells, particularly in pigmented basal cell tumors.

Experts agree that, though not innately aggressive in the majority of cases, BCC must be treated in a timely manner to avoid the subsequent necessity of more invasive treatment of the tumor and to preserve the surrounding normal tissue. It is estimated that PBCC constitutes 8 percent to 9 percent of all BCC, occurring more frequently in people with darker skin types.

Satoru Aoyagi, M.D., of the department of dermatology at Hokkaido University Graduate School of Medicine in Sapporo, Japan, conducted a novel study on BCC at the University of Miami Mohs Surgery Center, Miami, evaluating the surgical margins of pigmented and nonpigmented lesions following MMS, as well as the relative frequency with the histologic subtype of each PBCC.

In the study, 293 patients presented with a total of 345 biopsy-proven BCCs treated using MMS.

Study results showed that the pigmented lesions (67/345 or 19.4 percent) had a higher frequency of the nodular subtype (74.6 percent PBCC vs. 57.2 percent NPBCC), whereas the more aggressive morpheic type had a lower frequency (7.5 percent PBCC vs. 15.5 percent NPBCC), compared to the NPBCC group.

"We saw that the number of Mohs stages required to clear a tumor was positively less abundant in the PBCC group. The differences here were statistically significant and we could achieve a faster tumor clearance in pigmented lesions, compared to nonpigmented lesions. A total of 68.7 percent of all pigmented lesions required a 4 mm surgical margin to achieve tumor-free resection borders, whereas only 17.9 percent required margins greater than 5 mm," Dr. Aoyagi tells Dermatology Times.

Further study data of the total mean surgical margins showed a significant difference in tumor size (less than 2 cm) and histologic grading (the nonaggressive types) between pigmented and nonpigmented lesions. Dr. Aoyagi says that prior large-scale BCC studies show that the pigmentation in BCC depends on histologic subtype.

"In our study, the mean surgical margin of lesions in the smaller and less aggressive histologic subtypes of PBCC was smaller than compared to NPBCC, suggesting a relation between pigmentation and preclinical tumor invasion," he says.

According to Dr. Aoyagi, these study results help to better identify high-risk tumors with extensive subclinical invasion, which can be very helpful in providing optimal treatment, as well as in reducing morbidity and helping to keep healthcare costs low. Conversely, he says that identifying low-risk tumors can help preserve nonaffected perilesional tissue with high local control rates.

"Understanding the appropriate predictive surgical margin in relation to each predictive factor is important for surgical planning and the creation of guidelines for excision margins," Dr. Aoyagi says.

High visibility equals smaller margin

Dr. Aoyagi found that a smaller surgical margin is required for PBCC, as compared to the nonpigmented basal cell lesions.

This trend was particularly evident in smaller-sized BCCs as well as in the nonaggressive histologic subtype BCCs.

He says that the tumor borders in PBCC are often more evident to the surgeon because of the stark pigment seen. Also, a patient will more likely visit his or her dermatologist with a pigmented lesion as compared to a nonpigmented lesion, simply because a pigmented lesion is more visible and more worrisome to the untrained eye.

"This leads to the treatment of each tumor in the early growth stage. If a tumor is reported and treated early, there is a clear reduction in subclinical microscopic tumor invasion and smaller surgical margins in PBCC," Dr. Aoyagi concludes.