Three-Case Series Details Diagnostic Pitfalls in Borderline and Malignant Phyllodes Tumors

A three-case series from the Second Affiliated Hospital of Shandong First Medical University in Tai’an, China, published in Frontiers in Oncology, describes three women with borderline or malignant phyllodes tumors who declined preoperative core needle biopsy, with clinical underestimation of malignancy also contributing to the decision to proceed directly to excision. Phyllodes tumors can overlap with fibroadenomas both clinically and radiologically, and the authors report that incomplete preoperative characterization altered surgical planning in these cases, shifting key decisions to the operating room and to margin-directed re-excision.

The first patient was a 36-year-old woman with long-standing bilateral breast masses. She proved to have a 63-millimeter malignant phyllodes tumor with heterologous chondroid and osseous differentiation and osteoclast-like giant cells, meaning the tumor contained cartilage-like and bone-like tissue along with giant cells resembling osteoclasts. Two lesions on the opposite side were diagnosed as fibroadenomas.

An involved margin in this first patient prompted re-excision. No residual tumor was found, and the final closest histological margin measured 20 millimeters, which permitted breast conservation rather than mastectomy.

The second case involved a 68-year-old woman with a 75-millimeter malignant phyllodes tumor whose axillary imaging was internally discrepant: mammography showed mildly prominent ipsilateral axillary nodes, while axillary ultrasonography found no abnormal enlargement. Following a malignant phyllodes interpretation on frozen section, the planned wide local excision was converted to total mastectomy. Sentinel lymph node biopsy was negative, with zero of three nodes involved, and the closest margin was the deep margin at 20 millimeters. The patient declined postoperative radiotherapy.

The third patient was a 53-year-old woman with a previous right breast fibroadenoma excision. She had a right borderline phyllodes tumor involving the inked surgical margin, along with contralateral pseudoangiomatous stromal hyperplasia. Re-excision approximately 2 centimeters beyond the previous surgical margin found no residual tumor.

Across all three patients, postoperative wound healing was satisfactory, with no reported complications or recurrence during the reported 6-month follow-up period.

The authors state that these cases highlight the need for preoperative tissue diagnosis, attention to discrepant axillary imaging, individualized margin-directed surgery, and long-term surveillance. The frozen-section conversion in the second case illustrates how intraoperative pathology redirected surgery when no preoperative biopsy had been obtained, and the axillary imaging discrepancy in that same patient illustrates the kind of finding the authors flag for attention when planning nodal assessment.

As a case series, the report cannot establish how often such diagnostic pitfalls occur in the broader population of phyllodes tumors, and a 6-month follow-up cannot demonstrate long-term control of borderline or malignant disease, which the authors frame as requiring ongoing surveillance. The findings are limited to three patients at a single institution in China, and the outcomes described, including negative sentinel nodes, clear margins after re-excision, and absence of recurrence at 6 months, are observations from individual cases rather than estimates of treatment efficacy.

Within those limits, the series provides a concrete illustration of why the authors emphasize preoperative core needle biopsy for breast masses that may be phyllodes tumors, and why margin status, documented histologically, shaped the extent of surgery in every case reported.

Subject of Research: Diagnostic pitfalls and individualized surgical management of borderline and malignant phyllodes tumors of the breast

Article Title: Case Report: Diagnostic pitfalls and individualized surgical management of borderline and malignant phyllodes tumors: a three-case series

Article References: Wang, C., Liu, X., Wang, Y., & Miao, X. (2026). Case Report: Diagnostic pitfalls and individualized surgical management of borderline and malignant phyllodes tumors: a three-case series. Frontiers in Oncology, 16, Article 1966376. https://doi.org/10.3389/fonc.2026.1966376

Image Credits: AI Generated

DOI: 10.3389/fonc.2026.1966376

Keywords: phyllodes tumor, borderline phyllodes tumor, malignant phyllodes tumor, core needle biopsy, frozen section, surgical margin, sentinel lymph node biopsy, breast conservation, mastectomy, case series, diagnostic pitfall, breast surgery