Characterization of Basosquamous Cell Carcinoma: A Distinct Type of Keratinizing Tumour.

Basosquamous carcinoma is a rare clinical entity, which comprises 1.7-2.7% of all skin carcinomas. It is described as a basal cell carcinoma with features of squamous differentiation. To date, studies of the epidemiology of basosquamous carcinoma have been few and small in size. We report here the most extensive series of basosquamous carcinomas published to date, highlighting the differences between basosquamous carcinoma and other keratinizing tumours. Patients undergoing surgical excision for keratinizing tumours were enrolled in this study. Age, sex and tumour characteristics were recorded. A total of 1,519 squamous cell carcinomas, 288 basosquamous carcinomas and 4,235 basal cell carcinomas were collected. Basosquamous features were compared with those of basal cell and squamous cell carcinomas. For basosquamous carcinomas, 70.5% were located on the head and neck, particularly on the nose, forehead and cheeks, and represented almost 10% of the keratinizing tumours on the ears. Significant differences were found between basosquamous carcinoma and basal cell or squamous cell carcinomas. Basosquamous carcinoma should be considered a distinct type of keratinizing tumour with different anatomical, sex and age distributions.