Background: Basal cell carcinoma with mixed histology (BCC-MH) demonstrates more than one pathologic pattern of tumor. Appropriate therapy for the nonaggressive tumor subtype diagnosed from a superficial biopsy may not be adequate to treat the unsuspected aggressive tumor subtype, resulting in recurrent skin cancer.
Objective: We prospectively evaluated the incidence and characteristics of BCC-MH.
Methods: Mohs surgical sections were evaluated for BCC-MH.
Results: BCC-MH was observed in 43% (49/144) of cancers. Only 10% (5/49) of the biopsy reports from these cancers diagnosed BCC-MH. Most BCC-MH were previously untreated (90% [44/49] of tumors) and were located on the nose.
Conclusion: More than 40% of basal cell carcinomas referred for removal of the residual tumor were BCC-MH. An unsuspected aggressive pathologic pattern of growth may not be detected after a superficial biopsy. Subsequently, the cancer may recur if the initial treatment for the diagnosed nonaggressive tumor subtype is inadequate for the undiscovered aggressive carcinoma. Mohs micrographic surgery is recommended for BCC-MH treatment.