Two unusual tumors in a patient with xeroderma pigmentosum: atypical fibroxanthoma and basosquamous carcinoma

Xeroderma pigmentosum (XP) is a rare autosomal recessive disease, characterized by a genetic defect in DNA repair. The consequence is a high incidence of skin cancers on sun-exposed cutaneous surfaces of affected children. First lesions appear in the first years of life: telangiectasia, actinic keratosis and keratoacanthomas. Squamous cell and basal cell carcinomas are the most frequent neoplasms. We report the case of a 6-year-old girl affected with XP, who developed two unusual tumors: an atypical fibroxanthoma and a basosquamous carcinoma. In both tumors, immunohistochemical study showed abnormal accumulation of the p53 protein, suggesting the presence of mutation of the p53 tumor suppressor gene. Such p53 mutations may be ultraviolet (UV)-induced, as they are frequently observed in tumors occurring in XP.