Concordance in clearance reporting between immunostained frozen sections and traditional permanent paraffin sections for Lentigo Maligna treated with Mohs surgery.

Abstract

Background: Mohs Micrographic Surgery (MMS) has risen in popularity as a management option for treating Lentigo Maligna (LM) due to its ability to accurately detect subclinical spread while conserving tissue. The primary concern for opponents of MMS in Melanoma remains the difficulty associated with interpretation of frozen sections compared with traditional paraffin sections, this has been made easier with the advent of immunostaining. Objective(s): Our study aims to assess the concordance in clearance reporting of Lentigo Maligna in immunostained frozen sections compared with permanent paraffin sections and Haematoxylin and Eosin staining. Method(s): We conducted a retrospective analysis of 38 LM cases treated by MMS between 2017 and 2020 in Melbourne, Australia. Immunostained frozen sections were assessed by a Mohs surgeon while permanent paraffin sections were assessed by an external dermatopathologist. Result(s): We report 86% agreement in reporting of LM in immunostained frozen sections compared with permanent paraffin sections. In 5/38 cases, permanent paraffin sections were reported as clear for LM but the Mohs surgeon had detected positive margins, requiring further excision. Conclusion(s): For LM treated with MMS, there is a high agreement of clearance reporting between immunostained stained frozen sections and permanent paraffin sections without immunostaining however immunostained frozen sections may be more sensitive.