I read on https://www.medscape.com/answers/276624-100162/which-histologic-findings-are-characteristic-of-superficial-basal-cell-carcinoma (mirror):
Approximately 10-15% of all BCCs are of this type [superficial]. This is the most common pattern seen in BCCs of the shoulder.
Why is superficial basal cell carcinoma (BCC) the most common pattern seen in BCCs of the shoulder, even though only 10-15% of all BCCs are superficial?