Human pathology
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Case Reports
Invasive ductal breast cancer within a malignant phyllodes tumor: case report and assessment of clonality.
Invasive carcinomas arising within fibroepithelial tumors represent an uncommon manifestation of breast cancer. We report the case of a 70-year-old woman who underwent mastectomy for a malignant phyllodes tumor measuring 6 cm. Histological workup of the specimen revealed a high-grade invasive ductal carcinoma 2.5 cm in diameter within the phyllodes tumor. ⋯ Using multiplex polymerase chain reaction, a comparative allelotyping was performed with a panel of 11 microsatellite markers. The malignant stroma of the phyllodes tumor showed loss of heterozygosity at chromosome 16q23, 17q12, 17q25, and 22q13; the epithelial tumor component shared the loss of 16q23; whereas the invasive carcinoma had lost divergent alleles at 16q23, 17q12, and 17q25, indicating a lack of clonality between phyllodes tumor and invasive ductal carcinoma. Although our data are compatible with a previously postulated common origin of epithelial and stromal components of phyllodes tumors, the coexisting invasive ductal carcinoma appears to represent a true collision tumor.