Collision tumours: our recent experience

Collision skin lesions (CSL) are rare clinical and pathological entities, posing significant diagnostic and therapeutic challenges. These lesions comprise at least two distinct cell populations - benign and/or malignant neoplasms - that are adjacent yet clearly demarcated. CSL were categorized as collision tumours into three types: two benign lesions, one benign and one malignant lesion, and two malignant lesions, with the most common being basal cell carcinoma (BCC) and melanocytic naevus.

To analyse and present cases of collision skin lesions treated surgically in our Dermatosurgical Unit.

A retrospective review was conducted on patients treated in our unit in 2021-2022, excluding lesions arising from preexisting conditions or located at the same anatomical site but separable upon examination.

Out of 838 patients, 4 cases of collision tumours were identified: one with two benign lesions and three with one benign and one malignant lesion, all histologically confirmed.

Collision tumours, due to their rare occurrence and complex nature, represent a diagnostic challenge. Awareness and early detection, aided by dermoscopy, are crucial for effective management. Treatment should prioritize the more aggressive component of the tumour, with excisional biopsy being a favourable approach. Further research is needed to better understand the pathogenesis and optimize diagnostic and therapeutic strategies.