Basosquamous carcinoma and melanoma collision tumor in a child with xeroderma pigmentosum.

Xeroderma pigmentosum (XP) is a rare autosomal recessive genodermatosis associated with hypersensitivity to ultraviolet radiation (UVR), being due to defects involving the nucleotide excision repair pathway. Patients with XP are prone to develop multiple cutaneous neoplasms including non-melanoma skin cancers and melanoma. Collision tumors in patients with XP have been reported in the literature including the following lesions, actinic keratosis, basal cell carcinoma, squamous cell carcinoma, and in situ melanoma. Herein, we present a rare collision tumor composed of melanoma and basosquamous carcinoma in a 13-year-old XP patient and describe the dermoscopic features.