An unusual collision tumour masquerading as a basal cell carcinoma on the nose

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.