Breast collision tumor: malignant phyllodes tumor and synchronous ductal carcinoma, case report

Collision tumors are defined as the presence of two tumors with different histologies in the same organ. Associations of lymphoma, sarcomas, phyllodes tumors, and carcinomas have been described in the breast. Phyllodes tumors are fibroepithelial tumors that account for 1% of breast tumors. They are classified as benign, borderline, or malignant based on the characteristics of their mesenchymal component. In 1% of phyllodes tumors, breast carcinomas (in situ and infiltrating) have been described in their epithelial component, with a higher incidence in those with borderline and malignant behavior. Even rarer is the synchronous presentation of a phyllodes tumor and a carcinoma (without a transition zone), the origin of which is still uncertain. We present the case of a collision tumor that presents both forms: a malignant phyllodes tumor with carcinoma in situ in its epithelial component and an invasive carcinoma in another quadrant of the breast synchronously, treated in a hospital in Latin America.