title: An unusual collision tumour masquerading as a basal cell carcinoma on the nose.
abstract: When two or more cutaneous tumours coexist in a single lesion, it is known as a cutaneous collision or contiguous tumour. Various combinations of collisions have been described. Collision tumours often have misleading clinical and histological presentations, and can be a diagnostic challenge. Chondroid syringomas are mixed cutaneous tumours of dual origin, and like collision tumours, are often confused with the more commonly seen cutaneous lesions. As chondroid syringomas are rare, their involvement in collision tumours is an even more peculiar occurrence. We report an unusual case of a cutaneous collision tumour on the nose involving an intradermal naevus and chondroid syringoma. To the best of our knowledge, this is the first time such a combination is reported.
authors.affiliation: Department of Dermatology, Singapore. hweech@hotmail.com
authors.forename: Hwee Chyen
authors.initials: HC
authors.lastname: Lee
authors.forename: Ki Wei
authors.initials: KW
authors.lastname: Tan
authors.forename: Min Wee
authors.initials: MW
authors.lastname: Chia
authors.forename: Chee Seng
authors.initials: CS
authors.lastname: Sim
mesh_terms: D000368:Aged; D002280:Basal Cell Carcinoma / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D017492:Keratosis, Seborrheic / Q000473:pathology*; D009378:Neoplasms, Multiple Primary / Q000473:pathology*; D009508:Nevus, Pigmented / Q000473:pathology*; D009669:Nose Neoplasms / Q000175:diagnosis*; D012878:Skin Neoplasms / Q000473:pathology*