T. GreywalA. GoldenbergS. EimpunthS. B. JiangUniversity of California, San DiegoFaculty of Medicine, Siriraj Hospital, Mahidol University2020-01-272020-01-272019-01-01Journal of the European Academy of Dermatology and Venereology. (2019)14683083092699592-s2.0-85075766501https://repository.li.mahidol.ac.th/handle/20.500.14594/52219© 2019 European Academy of Dermatology and Venereology Background: Basal cell carcinoma with large subclinical extension (BCC-LSE) is a tumour whose extensive spread becomes apparent during Mohs surgery histopathology review. Not recognizing BCC-LSE preoperatively may result in a greater number of Mohs layers and in larger than anticipated postoperative defects. Objective: To evaluate the characteristics of BCC-LSE. Methods: This retrospective study reviewed BCC treated with Mohs surgery at a single academic surgical centre between March 2007 and February 2012. A total of 2044 cases met the criteria of BCC-LSE, which was defined as a lesion requiring at least three Mohs stages and a final surgical margin (difference between preoperative and postoperative measurements in either vertical or horizontal dimensions) of ≥1 cm. Results: In adjusted multivariable analysis, male sex (P=0.05), Fitzpatrick skin type I (P=0.002), history of prior BCC (P=0.003) and subtypes of basosquamous, metatypical, micronodular, infiltrative, morpheaform and sclerosing (P=0.005) remained significant BCC-LSE predictors. Conclusions: Demographic factors, including personal history of BCC, skin type, anatomic location, gender and age, in addition to tumour histologic subtype assessed through incisional biopsy, can help predict occurrence of BCC-LSE and assist physicians in optimizing preoperative assessment of surgical time and complexity.Mahidol UniversityMedicineArticleSCOPUS10.1111/jdv.15884