THE HETEROGENOUS NATURE OF IN-VIVO BASAL-CELL CARCINOMA

BACKGROUND. There have been nearly 70 different histologic subtypes of basal cell carcinoma (BCC) described. Some of the subtypes have been shown to have clinical relevance. The degree to which one type may mer ge to another, within the same tumor mass, has been poorly studied. OB JECTIVE. To determine if BCCs maintain biopsy histology throughout the entire architecture of the tumor. METHOD. Tumors were evaluated with a prospective histologic analysis of all primary BCCs using the Mohs ' 'removal in layers'' technique. All BCCs that required more than a sin gle Mohs stage to clear were included in analysis. RESULTS. One hundre d forty-nine tumors were examined. Fourteen of these were of mixed his tologic subtype on biopsy and were not included in the analysis. Six b iopsy specimens were inadequate to make a subtype diagnosis and were e xcluded from calculation. Of the remaining 129 tumors 59% maintained t heir biopsy diagnosis at first Mohs stage, and 49% at the second Mohs stage. Infiltrative tumors were the most likely to maintain their hist ologic subtype classification. Of the tumors that showed nodular BCC o n biopsy, 13% were infiltrative or micronodular at first Mohs stage. C ONCLUSION. While many BCCs demonstrate a single histological subtype, roughly 40% change in their microscopic appearance at the subclinical extension. This finding has the potential to alter therapy. (C) 1998 b y the American Society for Dermatologic Surgery, Inc. Dermatol Surg 19 98;24:881-884.