Basosquamous Cell Carcinoma: A Summary of the Definitions and Demographic, Clinical, Therapeutic, Histological, and Outcome Analysis of 20 Consecutive Basosquamous Cell Carcinomas in Comparison with 130 Basal Cell and 81 Squamous Cell Carcinomas in a

<b>Objectives</b>: To clarify the characteristics of Basosquamous cell carcinoma (BSC), this study compares demographic, clinical, therapeutic, histological, and outcome findings of BSCs with those of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). <b>Methods</b>: The authors classified various definitions of BSC into three groups: the broadest, modest, and narrowest definitions. This study adopted the narrowest definition (both BCC and SCC features with transition zones in between) due to its wide use, its adoption by the World Health Organization, and the least heterogeneous definition. From 2009 to 2018, 20 consecutive cases of BSC presented in a single institution, along with 130 cases of BCC and 81 cases of SCC. <b>Results</b>: The statistically different parameters of BSC compared to BCC or SCC were age (SCC > BSC, BCC), duration (BSC, BCC > SCC), unclear border (BSC > BCC, SCC), higher NCCN classification (BSC, SCC > BCC), safety margin (SCC > BSC > BCC), operation time (BSC, SCC > BCC), reconstruction (less primary closure in BSC than BCC), microscopic size (BSC, SCC > BCC), perineural invasion (BSC > BCC), free lateral margin (BSC, SCC > BCC), and follow-up period (BSC > BCC, SCC). Regarding outcome, one distant metastasis (6.3%) in BSCs, no aggressive consequences in BCCs, and four local recurrences (11.1%), two lymph node metastases (5.6%), and one distant metastasis (2.7%) in SCCs were observed. <b>Conclusions</b>: In this Asian cohort, BSC has a trend toward higher rates of overall adverse outcomes compared to BCC, although this difference did not reach definitive statistical significance, unlike the findings reported in Caucasian populations. Early detection and appropriate treatment at the individual patient level are warranted to minimize rare but clinically relevant adverse events and reproduce favorable outcomes at the population level. Wide local excision followed by local flaps could be a successful surgical option with an adequate safety margin and double histopathologic intraoperative and postoperative check-up.