Unusual collision tumor with infiltrating ductal carcinoma and breast skin squamous cell carcinoma: A case report and literature review.

Introduction: Breast cancer is the most common diagnosed cancer among women worldwide. Invasive ductal carcinoma (IDC) is the most common type, on the other hand, squamous cell carcinoma of the skin (SCC) overlying the breast is a rare tumor. The co-presence of two tumor types in one organ is even a rarer entity, termed as collision tumor.