Mohs yields low recurrence for BCC, SCC

Key Points

Adelaide, South Australia - Although little data is available on the recurrence rate of scalp tumors following Mohs micrographic surgery (MMS), according to one Mohs surgeon, the recurrence rate of scalp tumors treated with MMS, whether basal or squamous cell carcinoma, Bowen's disease or atypical fibroxanthoma, is very low.

Igal Leibovitch, M.D., of the oculoplastic and orbital division at the Royal Adelaide Hospital, University of Adelaide, South Australia, performed a prospective, non-comparative, multi-center study in which he analyzed recurrence rates of patients with scalp tumors who underwent MMS in Australia between 1993 and 2002.

Of the 316 patients (216 male and 100 female) in the study, 183 patients (57.9 percent) had basal cell carcinoma (BCC), 113 patients (35.8 percent) had squamous cell carcinoma (SCC), 13 patients (4.1 percent) had Bowen's disease (BD), 5 patients (1.6 percent) had atypical fibroxanthoma (AFX), one patient (0.3 percent) had microcystic adnexal carcinoma (MAC) and one patient (0.3 percent) had mucinous carcinoma.

Gender gap

"Although it is commonly accepted that BCC and SCC are the most common malignant nonmelanoma scalp tumors, there is a difference in the incidence and tumor type preponderance in relation to gender.

"In females, BCC is considered the most common scalp tumor, whereas SCC is much less common. In males, the relative incidence of SCC is higher than in females. In our analysis, the incidence of BCC and SCC in males was almost equal, whereas in females, the incidence of BCC was much higher than SCC," Dr. Leibovitch says.

He says that in the study, a five-year follow-up was available in 110 patients (34.8 percent). Twenty patients (6.3 percent) died of non-tumor related reasons, and 186 patients (58.9 percent) were lost to follow-up or could not be contacted.

Dr. Leibovitch cites a similar study by Katz et al in which 197 scalp tumors on females treated with MMS were analyzed, and which found that 77 percent of cases were BCC and only 17 percent were SCC. In this study, however, 39 percent of males' scalp tumors were BCC and 53 percent were SCC. This study showed a 3:1 male to female ratio in scalp tumors, which is in accordance with the 2:1 male to female ratio found in Dr. Leibovitch's study results.

"These findings in males and females are not fully elucidated, and could possibly stem from differences in the intensity of solar exposure - meaning outdoor occupations, sunbathing habits and the protective effects of hair or sun creams. It must be said, though, that our study is based on tumors referred to MMS, meaning that these tumors are categorized as high risk. Therefore, the clinical features, tumor types and gender distribution do not represent the true values of these variables in the general population," Dr. Leibovitch tells Dermatology Times.

He says the reason for the higher recurrence rate of BCC compared with SCC in the study remains unclear. He postulates that it may be due to a referral bias of more aggressive BCC tumors for Mohs surgery, and the incomplete five-year follow-up information on a significant number of cases.

Mohs choice tx

According to Dr. Leibovitch, surgical excision is the most frequent treatment modality for scalp tumors, and is considered the treatment of choice for most tumors.

He says that standard histological assessment of excision specimens with breadloaf sectioning examines only 0.2 percent of margins. Mohs micrographic surgery, on the other hand, examines close to 100 percent of the peripheral and deep margins.

"This is why it is generally accepted that MMS is indicated in high-risk tumors, defined as tumors which are recurrent or incompletely excised, larger than 2 cm in diameter, located in the mid-facial region, have an aggressive histology, and have perineural invasion," Dr. Leibovitch concludes.