Floaters in Mohs Micrographic Surgery

Background Floaters are dislodged pieces of tumor tissue than can obscure Mohs micrographic surgery (MMS) frozen sections and confound their interpretation. Objective To understand the common causes of floaters and identify management strategies. Methods An initial virtual consensus conference of Mohs surgeons based on a 60-item questionnaire. Data were validated in interviews with randomly selected Mohs surgeons. Results Based on retrospective reporting of 230 surgeon-years and 170,404 cases of MMS by 26 surgeons, the mean rate of floaters per tumor treated was 1.8%, and the rate of floaters per tissue block was 0.70%. Not wiping blades between cuts when a stage is separated into subunits can predispose to floaters. There was also strong consensus that basal cell carcinomas, ulcerated tumors, and tissue from the first stage were more likely to yield floaters. There is little consensus on how to manage floaters, with possibilities including taking additional sections, taking an additional stage, or simply noting the floater. Conclusion Floaters are not rare and can complicate MMS margin assessment. There is significant expert consensus regarding the causes of floaters and the tissue features that may predispose to them. Floaters may be prevented by minimizing their likely causes. There is less consensus on what to do with a floater.