Abstract
In collision situations, two or more different tumor cell populations proliferate in close proximity. Then, clinicaly, dermatoscopically and histopathologically, we find two different tumors next to each other.
The situations are rare and often very difficult from a diagnostic point of view. Different types of both benign and malignant skin cancers can collide together.
Particularly serious are situations where a malignant tumor is largely masked by a predominant benign tumor. Dermatoscopic examination enables to identify individual dermatoscopic structures of the examined lesion even in clinically difficult situations and to warn about the possibility of collision tumor.
We present three cases of collision (basal cell carcinoma/melanocyte nevus, basal cell carcinoma/seborrheic keratosis, melanocyte nevus/hemangioma) correlated with clinical, dermatoscopic and histopathological findings. We discuss the issue of collision tumors in practice.