A prospective study of the accuracy of the surgeon's diagnosis and significance of positive margins in nonmelanoma skin cancers.

Even with a precise preoperative diagnosis, complete excision of nonmelanoma skin cancer is not always achieved. The conundrum remains the decision for appropriate secondary treatment. Many surgeons, regardless of the nature of the lesion, consider re-excision to be the only option. In a prior 4-year prospective study that ascertained the accuracy of our clinical diagnosis of skin lesions removed in an office setting, one-fifth were found to be malignant and 98 percent (n = 415) of the lesions were nonmelanoma skin cancer. Unfortunately, 65 (15.7 percent) of the malignant nonmelanoma skin cancer lesions had positive margins. The outcome of our management for these specific lesions was followed prospectively over the 7.5 years of this study to determine whether aggressive surgical intervention was justified in every case. Of 65 patients with lesions, early and complete re-excision of margin-positive nonmelanoma skin cancer was performed for 34 (52.3 percent), with residual tumor found in 11 (32.4 percent), followed by a later recurrence in one (2.9 percent). The remaining 31 patients agreed to semiannual office visits, with one (3.2 percent) recurrence in this group. Thus, the overall rate of recurrence for margin-positive nonmelanoma skin cancer was 3.1 percent, with a mean follow-up of 3.6 years (range, 0 to 7.5 years). There were no recurrences for basal cell carcinoma in either treatment group, suggesting that, at least for "simple" primary lesions without confounding risk factors, there is some validity to a "wait and see" attitude, in which treatment of a potential recurrence would be straightforward. Despite our observed infrequent local recurrences of squamous cell cancers (13.3 percent), the small risk of metastases still suggests the appropriateness of complete surgical eradication for these tumors whenever feasible.