Tissue-Sparing Outcome of Mohs Micrographic Surgery in Squamous Cell Carcinomas.

Background: Micrographic Mohs Surgery (MMS) offers the highest cure rates and healthy skin tissue sparing effect compared with standard excision.

Objective: To quantify the tissue-sparing properties of MMS in squamous cell carcinoma (SCC) in comparison with standard excision (SE).

Methods: A bidirectional, descriptive study, including 94 cases of SCC, was performed, on patients with histologic diagnosis of SCC (in situ, well differentiated, moderately differentiated, and undifferentiated), that where operated with MMS between 2013 and 2018 at Hospital de Clínicas Dr. Manuel Quintela in Montevideo, Uruguay. Tumor size and defect area after MMS were measured in 2 perpendicular directions. The suspected defect area was calculated with standard excision using a 4-mm margin for low risk lesions and a 10-mm margin for high risk lesions. The primary outcome of this study was the size of the defect area post MMS compared with the calculated defect area with standard excision.

Results: The median tumor size was 1,41mm, and the median defect size after MMS was 4,12mm. The median defect size calculated for standard surgical excision was 8,36mm.

Limitations: We do not use all National Comprehensive Cancer Network (NCCN) criteria. We define low and high risk lesions just taking into account anatomical location, size, histopathology and whether it was a primary or recurrent tumor.

Conclusion: Our results show that MMS has a tissue-sparing effect of at least 52% compared to SE.