Multiple recurrent squamous cell carcinomas and utility of anticytokeratin immunohistochemistry

AE1/AE3: anti-pan cytokeratin 1/3 ART: adjuvant radiation therapy H&E: hematoxylin and eosin IHC: immunohistochemistry SCC: squamous cell carcinoma INTRODUCTION Mohs micrographic surgery remains the gold standard for the treatment of cutaneous squamous cell carcinomas (SCCs) of the head and neck. However, for recurrent or aggressive SCCs, it can be challenging at times to ensure complete margin control on hematoxylin and eosin (H&E) frozen sections alone. The authors present a case of multiple recurrent SCC that was ultimately found to have occult foci of tumor identifiable only by anticytokeratin immunohistochemistry (IHC). Although a large volume of literature addresses the topic of IHC for melanocytic neoplasms treated by traditional Mohs and ‘‘slow Mohs,’’ there is a relative paucity of commentary on its use in SCCs. This unusual case highlights the importance of anticytokeratin IHC for SCCs, especially in tumors that are recurrent or have aggressive or atypical cytomorphology.