Combined Mohs Micrographic Surgery in a Collision Tumor.

We present the case of a 73-year-old male patient with a collision tumor in the right ear, consisting of a basal cell carcinoma and melanoma in situ. He was managed with Mohs micrographic surgery combining paraffin-embedded sections and frozen sections. Multiple surgical stages were required to obtain tumor-free margins. The surgical defect was reconstructed by plastic surgery, achieving the preservation of the ear. The technique of combining two processing sections is useful in the treatment of the collision of basal cell carcinoma with malignant melanoma.