Frozen section and Mohs micrographic surgery techniques. A, To prepare a frozen section, the surgeon excises lesions with a surgical margin. For an eyelid margin lesion, the surgeon performs a wedge eyelid resection. The pathologist samples the nasal (N), temporal (T), and inferior margins. A central cross section (C) demonstrates the distance of the tumor from the inferior surgical margin. Similarly, an elliptical excision of the tumor can be evaluated by the bread-loaf technique in which multiple cross sections (C) are prepared. B, In Mohs micrographic surgery performed on an eyelid margin tumor, the surgeon excises the visible lesion. Then, additional thin shavings of tissue are prepared from the bed of the residual defect, allowing the surgeon to evaluate en face margins (EF). In another variation of Mohs surgery, the surgeon performs an elliptical excision of the visible tumor. Frozen en face (EF) sections are obtained from the undersurface and the edges of the excised lesion. The tumor locations are marked on a map for a subsequent second-stage excision.