Duplicitous growth of infiltrative basal cell carcinoma: Analysis of clinically undetected tumor extent in a paired case-control study.

BACKGROUND Many clinicians believe infiltrative basal cell carcinoma (BCC) is a more difficult tumor to eradicate than nodular BCC because the growth of infiltrative BCC is not easy to detect clinically. However, data supporting this observation are largely anecdotal. OBJECTIVE Our purpose was to show that infiltrative BCC have wider and deeper tumor extensions than nodular BCC of similar clinical size. METHODS In this retrospective study, 139 cases of infiltrative BCC excised by Mohs micrographic surgery (MMS) were matched to a control group of 139 cases of nodular BCC similarly excised. They were paired by site, size, number of recurrences, age, gender, and previous treatment type. The cases were selected and paired by computer from 1197 consecutive BCC (primary and recurrent) referred for MMS over a 5-year period. MMS technique allowed us to quantitate the extent of tumor spread using three measurements: the number of surgical stages required for complete removal of tumor, the width of tissue required to remove subdinical extension of tumor, and the depth of defect at completion of MMS. RESULTS Analysis showed the infiltrative BCC was more difficult to detect and to eradicate than the nodular BCC. The number of surgical stages required for complete removal of tumor, the width of tissue required to remove subclinical extension of tumor, and the depth of defect at completion of MMS were all greater with infiltrative BCC when compared with nodular BCC regardless of whether cases mere primary or recurrent. These differences were all statistically significant. CONCLUSION Infiltrative BCC can be significantly more destructive than nodular BCC because tumor extension is difficult to detect clinically. Clinicians should treat infiltrative BCC with its potential for covert invasion in mind.