The Impact of Radiotherapy and Histological Risk Factors on Outcomes in Malignant Phyllodes Tumors

The Defect Repair After a Giant Malignant Phyllodes Tumor Resection of Breast Using a Kiss Flap

Malignant phyllodes tumors of the breast are fairly rare and fast-growing tumors. They are not sensitive to chemotherapy or hormonal therapy. Therefore, the primary treatment for malignant phyllodes tumors is wide surgical excision. Herein, we report a case study which featured a 26-year-old woman presented with a giant malignant phyllodes tumor measuring 20 × 17 × 13 cm. In order to reduce the chance of local recurrence, treatment for these types of tumors usually involves extensive excision with at least 1 cm of surgical margins. The patient underwent mastectomy with negative surgical margins, which left a large skin defect of 25 × 15 cm. Repair of such a large skin defect is a challenge to breast surgeons. This is the first reported case in which a “kiss” flap was successfully used to repair the skin defect created after resection of a giant malignant phyllodes tumor. The kiss flap could be considered as an effective and simple method to repair large chest wall defects after resection of giant phyllodes tumors.

Therapeutic and immunomodulatory potential of pazopanib in malignant phyllodes tumor

Malignant phyllodes tumors (PT) are rare aggressive fibroepithelial neoplasms with high metastatic potential and lack effective therapy. We established a patient-derived xenograft (PDX) and cell line model (designated MPT-S1) of malignant PT which demonstrated clinical response to pazopanib. Whole exome sequencing identified somatic mutations in TP53, RB1, MED12, and KMT2D. Immunohistochemistry and genomic profiles of the tumor, PDX and cell line were concordant. In keeping with clinical observation, pazopanib reduced cell viability in a dose-dependent manner and evoked apoptosis, and led to significant abrogation of in vivo tumor growth. Whole transcriptomic analysis revealed that pazopanib decreased expression of genes involved in oncogenic and apoptosis signaling. We also observed decreased expression of ENPP1, with known roles in cancer invasion and metastasis, as well as STING pathway upregulation. Accordingly, pazopanib induced micronuclei formation, and evoked phospho-TBK1 and PD-L1 expression. In an additional cohort of malignant PT (n = 14), six (42.9%) showed comparable or higher levels of ENPP1 relative to MPT-S1, highlighting its potential role as a therapeutic target. In conclusion, we established MPT-S1, a new PDX and cell line model, and provided evidence for the clinical efficacy of pazopanib in malignant PT.