Adjuvant cytokeratin staining in Mohs micrographic surgery for basal cell carcinoma

Mohs micrographic surgery (MMS) is a technique that offers excellent cure rates in the treatment of basal cell carcinoma (BCC). One of the reasons for its success is the 100% visualization of the resection margins. Still, recurrences do occur in 2% to 5% of the treated BCCs. It has been suggested that BCC cells in frozen sections stained with hematoxylin and eosin (H&E) may be missed. To determine whether an additional immunohistochemical staining with a cytokeratin marker (MNF 116) indicates BCC cells in sections in which the H&E-stained frozen sections were negative. The Mohs procedure was performed under standard conditions in which H&E-stained slides were judged by the Mohs surgeon and the pathologist. After the H&E slides where judged negative, an extra slide was stained using immunohistochemistry and a monoclonal antibody against cytokeratin (MNF 116). A total of 143 complete slides were stained and judged by two Mohs surgeons and a pathologist. One of the 143 slides stained with MNF 116 showed positive staining where the H&E slides were negative, which is 0.7% of the slides. However, this single slide represents a failure of nearly 2% of the treated patients. Frozen sections stained with H&E in MMS offer enough security in detecting BCC cells during surgery; however, adjuvant cytokeratin staining can be useful in very selected cases of aggressive growing BCC