Subclinical Infiltration of Basal Cell Carcinoma in Asian Patients: Assessment after Mohs Micrographic Surgery

BACKGROUND Several differences in basal cell carcinomas (BCCs) were found, according to the ethnic group; for example, pigmented BCCs was more common in Asian or Hispanic patients. However, there are few reports on the subclinical extension of the BCC in Asian patients. OBJECTIVE The aim of this study was to evaluate the subclinical infiltration of the basal cell carcinoma in Asian patients. METHODS All patients with BCC who visited the department of dermatology at Korea University Ansan Hospital were treated with Mohs micrographic surgery. In 81 patients, 83 tumors of BCC were completely eradicated by Mohs micrographic surgery (MMS) from April 2001 to August 2008, and were reviewed in this study. Information recorded included the total margin and the number of stages of Mohs micrographic surgery, anatomic location, tumor size, presence of pigmentation, clinical type, and pathological subtype. We divided the clinical types into nodular, ulcerated, and pigmented, and the pathological types into nodular, micronodular, morpheaform, and adenoid. The BCC was of pigmented type if pigmentation covered more than 25% of the tumor, regardless of whether pigmentation was distinct, or if there was apparent pigmentation that covered more than 10% of the tumor. RESULTS The nose and cheek were the most common sites requiring more than one stage of surgery. In tumors smaller than 1 cm, 91.7% required only one stage of excision, compared with 60.6% in tumors larger than 1 cm. More than two Mohs stages were required in 25% of non-ulcerated BCCs and in 46.2% of ulcerated BCCs. Sixty eight percent of pigmented BCCs required only one stage of Mohs micrographic surgery. In cases of non-pigmented BCCs, only 45% required one Mohs stage. More than one Mohs stage was required in 19.2% of non-aggressive BCCs and in 42.9% of aggressive BCCs. CONCLUSION Subclinical infiltration differed between the two groups according to the size of the BCC (1 cm threshold) and most of the BCCs were located in the head and neck area. Considering this result, indication for MMS can be extended for BCCs larger than 1 cm in Asian patients. Ulcerated BCCs required more Mohs stages than non-ulcerated BCCs. Pigmented BCCs might show lesser subclinical infiltration than non-pigmented BCCs. Aggressive pathological subtypes showed more subclinical infiltration than the non-aggressive types; however, after evaluation of the border that was excised with MMS, mixed histologic types were found to be more frequent than generally accepted. Therefore, we consider that, when planning surgery, dermatologists should not place too much confidence in the pathologic subtypes identified by biopsy.