Using en face ink to guide the conservative sectioning of a Mohs margin.

Background: While the epidermal rim of a Mohs layer routinely requires some manipulation, the deep margin seems to conform easily to a smooth surface for sectioning even when tissue textures and contours are prominent. How well these common features of the deep margin flatten during processing has not been well studied.

Objective: To determine how successfully tissue processing flattens the deep margin of Mohs specimens.

Methods: Using en face inking, this study compared the sectioning required to reach a completed epidermal margin with that of the completed deep margin in 100 routine first-stage Mohs specimens.

Results: A mean of 248.8 μm of additional sectioning beyond the completed epidermal margin was required in 74% of specimens to reach the completed deep margin. This deep margin differential was associated with increasing layer size (p = .003) and those specimens that required the least amount of sectioning to reach a completed epidermal margin (p < .001).

Conclusions: The differential between the epidermal and deep margin suggests that tissue texture and contour irregularities can be easily compressed and internalized during embedding. En face inking can be used to delineate the tissue texture and surgical features of a Mohs margin ensuring a complete and conservative section evaluation.