Current clinical practice in the management of phyllodes tumors of the breast: an international cross-sectional study among surgeons and oncologists

Malignant Mesenchymal Tumors of the Breast: Current Challenges and New Perspectives on Primary Sarcomas and Malignant Phyllodes Tumors

Mesenchymal tumors of the breast constitute a rare and heterogeneous group of neoplasms, representing only 0.5% to 1% of all breast tumors. Originating from mesenchymal tissues, these tumors include various histological subtypes. They are particularly aggressive, characterized by a high propensity for local recurrence and an overall poor prognosis. The rarity of these cases has impeded the development of comprehensive clinical studies, leading to a lack of standardized diagnostic protocols and treatment guidelines. This review provides a thorough synthesis of current knowledge on breast mesenchymal tumors with a specific focus on malignant variants such as phyllodes tumors and breast sarcomas. It also addresses the diagnostic challenges faced by clinicians, evaluates current therapeutic strategies, and emphasizes the crucial role of surgical treatment. Additionally, it examines the evolving roles of chemotherapy and radiotherapy in enhancing patient outcomes.

Phyllodes Tumor of the Breast: Histomorphological Transformation to High-Grade Tumor during Pregnancy and Challenging Oncoplastic Surgery

Introduction

Phyllodes tumors of the breast are a very rare tumor entity. There are two different classifications according to AFIP (low-grade and high-grade phyllodes tumors of the breast) and WHO (three subtypes: benign, borderline, and malignant phyllodes tumors). Phyllodes tumors have an increased risk of recurrence. Primary clinical treatment of phyllodes tumors is surgery, although the width of the required resection margins often presents a challenge for surgical management.

Case Presentation

This case report deals with a 24-year-old woman with second recurrence of borderline phyllodes tumor. The challenge of this case lays first in surgical removal of the large tumor by breast-conserving therapy with tumor-free margins and favorable aesthetic outcome. Achieving this goal by tumor-adapted reduction mammoplasty, skin excision, and slide-swing skin flap was challenging. The second exciting aspect of this case is the histomorphology of the tumor and the transformation in vivo from fibroadenoma with stromal atypia in 2021 to the first recurrence with a low-grade phyllodes tumor in 2022 and the further transformation to a high-grade tumor with stromal overgrowth in the second recurrence of phyllodes tumor in 2023 during pregnancy and childbed.

Conclusion

This case of a phyllodes tumor shows how quickly tumor characteristics can change in fast-growing tumors due to transformation from low-grade to high-grade tumor. The influence of pregnancy on this process remains unclear at present. Surgical removal of phyllodes tumors should be performed during pregnancy.

Optimizing imaging modalities for sarcoma subtypes in radiation therapy: State of the art

The choice of imaging modalities is essential in sarcoma management, as different techniques provide complementary information depending on tumor subtype and anatomical location. This narrative review examines the role of imaging in sarcoma characterization and treatment planning, particularly in the context of radiation therapy (RT). Magnetic resonance imaging (MRI) provides superior soft tissue contrast, enabling detailed assessment of tumor extent and peritumoral involvement. Computed tomography (CT) is particularly valuable for detecting osseous involvement, periosteal reactions, and calcifications, complementing MRI in sarcomas involving bone or calcified lesions. The combination of MRI and CT enhances tumor delineation, particularly for complex sites such as retroperitoneal and uterine sarcomas, where spatial relationships with adjacent organs are critical. In vascularized sarcomas, such as alveolar soft-part sarcomas, the integration of MRI with CT or MR angiography facilitates accurate mapping of tumor margins. Positron emission tomography with [18 F]-fluorodeoxyglucose ([18 F]-FDG PET) provides functional insights, identifying metabolically active regions within tumors to guide dose escalation. Although its role in routine staging is limited, [18 F]-FDG PET and emerging PET tracers offer promise for refining RT planning. Advances in artificial intelligence further enhance imaging precision, enabling more accurate contouring and treatment optimization. This review highlights how the integration of imaging modalities, tailored to specific sarcoma subtypes, supports precise RT delivery while minimizing damage to surrounding tissues. These strategies underline the importance of multidisciplinary approaches in improving sarcoma management and outcomes through multi-image-based RT planning.

Patient-derived organoid models of malignant phyllodes tumours for drug sensitivity testing and identification of targeted therapeutic strategies

BACKGROUND

Malignant phyllodes tumours (MPT) of the breast are rare fibroepithelial neoplasms. It exhibits rapid growth, large size, and a high local recurrence rate.

METHODS

In this study, we established novel patient-derived organoid (PDO) models from two primary MPT samples and conducted comprehensive genetic profiling and drug screening.

RESULTS

The PDO models faithfully recapped the histopathological and molecular features of the primary tumours, including stromal overgrowth, leaf-like projections, and the expression of key diagnostic markers. Drug testing revealed significant heterogeneity in response profiles to chemotherapeutic reagents between the two MPT-derived organoids, implying the importance of personalised drug testing. Next-generation sequencing analysis identified recurrent mutations in TP53, RB1, EGFR, ATM, and RECQL4, which correlated with the drug sensitivity profiles observed in the organoid models. Targeted therapeutic drugs, such as Abemaciclib (targeting the RB1 pathway) with an IC50 value of 1.744 µM, and Alflutinib Mesylate (targeting the EGFR pathway) with an IC50 value of 0.9150 µM, exhibited significant cytotoxic effects in the MPT2 organoid models.

CONCLUSIONS

This study highlights the novel application of PDOs for studying the molecular landscape of MPTs and identifying effective therapeutic targets, offering a promising platform for guiding personalised treatment strategies for this rare and challenging cancer.

Case report: rapid growth of malignant phyllodes tumor

Phyllodes tumors (PT) are exceedingly rare fibroepithelial neoplasms that arise from breast stromal tissue, primarily occurring in women in the fourth and fifth decade. This poses a diagnostic challenge among younger women with breast masses, such as those in their late teens to early thirties, where benign breast masses such as fibroadenomas are more common. In this report, a 19-year-old female presented with a rapidly enlarging complex mass of the right breast over the course of two months. An ultrasound revealed a mass measuring 19 × 17 × 23 cm, with multiple solid and cystic components. The mass was classified as BI-RADS 4. Due to the continuous growth, the patient underwent total right mastectomy. Final pathology revealed a malignant phyllodes tumor measuring 24 × 12 × 7 cm with cystic component. Phyllodes tumor management remains complex, requiring a tailored multidisciplinary approach based on individual tumor characteristics and patient factors.

UK guidelines for the management of soft tissue sarcomas

Soft tissue sarcomas (STS) are rare tumours arising in mesenchymal tissues and can occur almost anywhere in the body. Their rarity, and the heterogeneity of subtype and location, means that developing evidence-based guidelines is complicated by the limitations of the data available. This makes it more important that STS are managed by expert multidisciplinary teams, to ensure consistent and optimal treatment, recruitment to clinical trials, and the ongoing accumulation of further data and knowledge. The development of appropriate guidance, by an experienced panel referring to the evidence available, is therefore a useful foundation on which to build progress in the field. These guidelines are an update of the previous versions published in 2010 and 2016 [1, 2]. The original guidelines were drawn up by a panel of UK sarcoma specialists convened under the auspices of the British Sarcoma Group (BSG) and were intended to provide a framework for the multidisciplinary care of patients with soft tissue sarcomas. This iteration of the guidance, as well as updating the general multidisciplinary management of soft tissue sarcoma, includes specific sections relating to the management of sarcomas at defined anatomical sites: gynaecological sarcomas, retroperitoneal sarcomas, breast sarcomas, and skin sarcomas. These are generally managed collaboratively by site specific multidisciplinary teams linked to the regional sarcoma specialist team, as stipulated in the recently published sarcoma service specification [3]. In the UK, any patient with a suspected soft tissue sarcoma should be referred to a specialist regional soft tissues sarcoma service, to be managed by a specialist sarcoma multidisciplinary team. Once the diagnosis has been confirmed using appropriate imaging and a tissue biopsy, the main modality of management is usually surgical excision performed by a specialist surgeon, combined with pre- or post-operative radiotherapy for tumours at higher risk for local recurrence. Systemic anti-cancer therapy (SACT) may be utilised in cases where the histological subtype is considered more sensitive to systemic treatment. Regular follow-up is recommended to assess local control, development of metastatic disease, and any late effects of treatment.

A Rare Case of Benign Phyllodes Tumor of the Breast Responding to Anastrozole

A phyllodes tumor is a rare fibroepithelial breast tumor that can be benign, borderline, or malignant. Its diagnosis is challenging because it shares characteristics with other lesions. The treatment is primarily surgical, with no established role for chemotherapy and limited evidence supporting radiotherapy. There is no evidence of phyllodes tumors expressing endocrine receptors, nor is there an established role for endocrine therapy in treating these tumors. We present a case of a large phyllodes tumor that showed a clinical response to treatment with anastrozole.

Genomic Landscape of Malignant Phyllodes Tumors Identifies Subsets for Targeted Therapy

PURPOSE

Malignant phyllodes tumors (MPTs) are rare fibroepithelial tumors of the breast with aggressive biologic behavior and high recurrence rates. Surgery remains the primary treatment modality for these tumors; however, initial investigations suggest a potential for targeted therapies in managing this disease. Therefore, we aimed to assess the molecular landscape of MPTs to reveal possible treatment opportunities.

METHODS

MPTs (n = 57) from primary and metastatic sites underwent genomic sequencing (592-gene panel or whole exome), whole-transcriptome sequencing, and immunohistochemistry (PD-L1, human epidermal growth factor receptor 2 [HER2]) at Caris Life Sciences (Phoenix, AZ). Immune cell fractions in the tumor microenvironment were estimated using quanTIseq. Mann-Whitney U, chi-square, and Fisher's exact tests were used to determine significance (P < .05).

RESULTS

MPTs had low ERBB2 expression, comparable with the HER2-negative subset of a large cohort of breast adenocarcinoma samples (N = 9,926). Frequent alterations included TERT promoter; MED12, TP53, and NF1 mutations; and less frequently EGFR, PIK3CA, and BRAF. Differences in mutation prevalences were observed between primary sites, lung metastases, and nonlung metastases. One MPT specimen harbored a pathogenic TPM4:NTRK1 fusion, and treatment with larotrectinib for over 16 months suggested a clinical response to therapy. PD-L1+ status was observed in 15.2% of MPTs overall, with similar prevalence in primary sites and lung metastases. B cells, M2 macrophages, neutrophils, and natural killer cells had the highest median cell fractions in MPTs.

CONCLUSION

Considering the occurrence of several actionable alterations including a TPM4:NTRK1 fusion reported herein, these results support the use of next-generation sequencing (NGS) including RNA analysis for fusion detection to identify such alterations in patients with MPTs. These findings highlight the importance of comprehensive NGS in MPT research to uncover potential targeted treatment options for these patients.

Deep learning-assisted distinguishing breast phyllodes tumours from fibroadenomas based on ultrasound images: a diagnostic study

OBJECTIVES

To evaluate the performance of ultrasound-based deep learning (DL) models in distinguishing breast phyllodes tumours (PTs) from fibroadenomas (FAs) and their clinical utility in assisting radiologists with varying diagnostic experiences.

METHODS

We retrospectively collected 1180 ultrasound images from 539 patients (247 PTs and 292 FAs). Five DL network models with different structures were trained and validated using nodule regions annotated by radiologists on breast ultrasound images. DL models were trained using the methods of transfer learning and 3-fold cross-validation. The model demonstrated the best evaluation index in the 3-fold cross-validation was selected for comparison with radiologists' diagnostic decisions. Two-round reader studies were conducted to investigate the value of DL model in assisting 6 radiologists with different levels of experience.

RESULTS

Upon testing, Xception model demonstrated the best diagnostic performance (area under the receiver-operating characteristic curve: 0.87; 95% CI, 0.81-0.92), outperforming all radiologists (all P < .05). Additionally, the DL model enhanced the diagnostic performance of radiologists. Accuracy demonstrated improvements of 4%, 4%, and 3% for senior, intermediate, and junior radiologists, respectively.

CONCLUSIONS

The DL models showed superior predictive abilities compared to experienced radiologists in distinguishing breast PTs from FAs. Utilizing the model led to improved efficiency and diagnostic performance for radiologists with different levels of experience (6-25 years of work).

ADVANCES IN KNOWLEDGE

We developed and validated a DL model based on the largest available dataset to assist in diagnosing PTs. This model has the potential to allow radiologists to discriminate 2 types of breast tumours which are challenging to identify with precision and accuracy, and subsequently to make more informed decisions about surgical plans.

Retrospective analysis of core-needle and vacuum-assisted breast biopsies of B3 fibroepithelial lesions and correlation with results in subsequent surgical specimens

BACKGROUND

Fibroepithelial lesions (FEL) are a heterogeneous group of biphasic tumours that include fibroadenomas (FA) and the rare entity of benign phyllodes tumors (PT) as well as cases where distinction between these two entities is not possible. The histologic distinction between benign PT and cellular FA is still a diagnostic challenge, especially in core-needle biopsy (CNB) or vacuum-assisted biopsy (VAB). Guidelines are not clearly established regarding the management of FEL in CNB or VAB. In this study, we addressed the frequency of B3 FEL diagnosed in CNB or VAB and compared the final histopathological findings in the excision specimens to evaluate up- or downgrading.

METHODS

We identified 117 female patients with the preoperative diagnosis of FEL (B3), PT, or FEL in combination of pure epithelial B3 lesions in CNB or VAB. Clinico-pathological information as well as data on subsequent surgical excision were available for all patients.

RESULTS

PT was diagnosed in 9 (14.8%) and FEL (B3) in 52 (85.2%) cases. Additionally, 56 patients with FA in combination with an additional B3 lesion were identified. Most FEL (B3)/PT initial diagnoses were made in CNB (55.6% of PT; 84.6% of FEL). After the initial biopsy, 7 of 9 (77.8%) patients with initial diagnosis of benign or borderline PT in CNB/VAB and 40 of 52 (77.0%) patients with initial diagnosis of FEL (B3) in CNB/VAB underwent open excision (OE). 4 of 9 cases (44.4%) initially diagnosed as PT were verified, whereas 2 of 9 (22.2%) were downgraded to FA. 20 of 52 cases (38.5%) initially diagnosed as FEL (B3) were downgraded to FA, whereas 11 of 52 cases (21.2%) were diagnosed as benign or borderline PT. One FEL (B3) case was upgraded to malignant PT.

CONCLUSION

Most PT and FEL (B3) diagnoses on CNB/VAB underwent surgical removal. In the final pathological findings of cases classified primarily as FEL (B3), the majority were downgraded to FA, one quarter were upgraded to PT, and a small subset remained as combined FA/PT. In clinical daily practice, we recommend individualized decision-making considering different options (clinical follow-up or removal of the lesion depending on the whole context) in a multidisciplinary preoperative conference.

Malignant phyllodes tumor of the breast with predominant osteosarcoma and chondrosarcomatous differentiation: a rare case report and review of literature

Background

Phyllodes tumors (PTs), which account for less than 1% of mammary gland tumors, composed of both epithelial and stromal components. If a malignant heterologous component is encountered, PT is considered malignant. Malignant phyllodes tumors (MPTs) only account for 8% to 20% of PTs. We report a case of MPT with osteosarcoma and chondrosarcoma differentiation and review the literature to discuss the differential diagnosis and therapy.

Case presentation

A 59-year-old Chinese woman come to our hospital because of a palpable mass she had had for 1 months in the left breast. Preoperative core needle biopsy (CNB) was performed on the left breast mass on January 11, 2023. Pathological diagnosis was malignant tumor, the specific type was not clear. Mastectomy and sentinel lymph node biopsy of the left breast was performed. No metastasis was found in 3 sentinel lymph nodes identified by carbon nanoparticles and methylene blue double staining. Heterologous osteosarcoma and chondrosarcomatous differentiation of phyllodes tumor were observed. Immunohistochemistry: spindle tumor cells ER(-), PR(-), HER-2(-), CK-pan(-), CK7(-), CK8(-), SOX10(-), S100(-), and MDM2(-), CK5/6(-), P63(-), P40(-) were all negative. CD34:(+), SATB2(+), P53(90% strong), CD68 (+), Ki-67(LI: about 60%). No ductal carcinoma in situ was found in the breast. Fluorescence in situ hybridization (FISH) indicated USP6 was negatively expressed on formalin-fixed, paraffin-embedded (FFPE) tissue sections.

Conclusion

MPTs are rare, and heterologous differentiation in MPTs is exceedingly rare. It could be diagnosed by pathology when metaplastic carcinoma, primary osteosarcoma, or myositis ossificans were excluded. This case could help clinicians to improve the prognosis and treatment of this disease.

Real-world data on malignant and borderline phyllodes tumors of the breast: A population-based study of all 921 cases in the Netherlands (1989 -2020)

AIM

The aim of our study is to analyze patterns in treatment and outcome in a population-based series of patients with borderline and malignant phyllodes tumors (PT).

MATERIAL AND METHODS

Data on all patients with a borderline or malignant PT (1989-2020) were extracted from the Netherlands Cancer Registry and the Dutch nationwide pathology databank (Palga) and retrospectively analyzed.

RESULTS

We included 921 patients (borderline PT n = 452 and malignant PT n = 469). Borderline PT patients more often had breast-conserving surgery (BCS) as final surgery (81 vs. 46%). BCS rates for borderline PT increased over time (OR 1.08 per year, 95%CI 1.04 - 1.13, P < 0.001). In malignant PT adjuvant radiotherapy was given in 14.7%; this rate increased over time (OR 1.07 per year, 95%CI 1.02 - 1.13, P = 0.012). Local recurrence rate (5-year estimate of cumulative incidence) was 8.7% (95%CI 6.0-11.4) for borderline PT and 11.7% (95%CI 8.6-14.8) for malignant PT (P = 0.187) and was related to tumor size ≥ 20 mm (HR 10.6 (95%CI 1.5-76.8) and positive margin (HR 3.0 (95%CI 1.6-5.6), p < 0.001), but not to negative margin width (HR 1.3 ( 95%CI 0.7-2.3), p = 0.350)). Distant metastasis occurred only in malignant PT with a 5-year cumulative incidence of 4.7% (95%CI 3.3 - 6.1).

CONCLUSION

This population-based series showed an increase in BCS in borderline PT and an increase in adjuvant radiotherapy in malignant PT over time. We identified malignant PT, BCS, larger tumor size and positive final margins as possible risk factors for local recurrence. Small but negative margins can be accepted.

Challenges and Clinical Relevance of Modern Breast Pathology Reporting: Your Questions Answered

BACKGROUND

Breast pathology reporting, especially for breast cancer, has evolved through the years, from terse succinct diagnostic conclusions with scant histological details to the current comprehensive reporting guidelines issued by major pathology colleges and bodies, including the International Collaboration on Cancer Reporting. Pathology elements included in reporting guidelines are evidence based and contribute significantly to individualised and personalised patient management.

SUMMARY

This article is based on the lively interactive question and answer session that followed the breast pathology segment in the symposium jointly organised by the British Association of Urological Pathology, British Association of Gynaecological Pathologists, British Society of Gastroenterology and the Association of Breast Pathology, in November 2022, titled "Personalised histopathology reporting for personalised medicine."

KEY MESSAGES

The breast pathology session emphasised the clinical utility of breast pathology data items, incorporating a case-based approach by highlighting the relevance of pathology information in various clinical scenarios. This review included clinico-pathological discussion points on florid lobular carcinoma in situ, atypical apocrine adenosis, post-neoadjuvant chemotherapy reporting, atypical ductal hyperplasia presenting at the margin, flat epithelial atypia versus columnar cell change, papilloma on core needle biopsy, margin status, mucocele-like lesion, total duct excision/microdochectomy specimen, and anterior and nipple margins in skin-sparing mastectomy. Effective communication and regular involvement of pathologists in breast multidisciplinary tumour boards are crucial.

Multidisciplinary Management of Phyllodes Tumours and Breast Sarcoma: A Cross-sectional Survey of Clinical Practice across the UK and Ireland

AIMS

Phyllodes tumours and breast sarcomas are uncommon tumours and their rarity poses significant challenges in diagnosis and management. This cross-sectional study was conducted to evaluate the multidisciplinary clinical practice for these tumours across the UK and Ireland, with the aim of identifying gaps in knowledge and providing direction for establishing national guidelines.

MATERIALS AND METHODS

An international survey was adapted and circulated to breast and/or sarcoma surgeons and oncologists in the UK and Ireland through national organisations. Multidisciplinary team (MDT) responses were analysed anonymously.

RESULTS

Twenty-eight MDTs participated in this study, predominately from high-volume units (85.5%). Although only 43% of the surveyed units were part of a trust that holds a sarcoma MDT, 68% of units managed malignant phyllodes and angiosarcoma, whereas 64.5% managed soft-tissue sarcoma of the breast. Across all subtypes, axillary surgery was recommended by 14-21% of the MDTs and the most recommended resection margins for breast surgery were 'no tumour on ink' in benign phyllodes (39%) and 10 mm in the remaining subtypes (25-29%). Immediate breast reconstruction was supported by 11-18% of MDTs for breast sarcoma subtypes, whereas 36% and 32% advocated this approach in benign and borderline phyllodes tumours, respectively. Adjuvant radiotherapy and chemotherapy were recommended by up to 29% and 11% of the MDTs, respectively.

CONCLUSION

The results of this study demonstrate a wide variation in clinical practice across the surveyed MDTs. As only 28 MDTs participated in our study, with under-representation from low-volume units, our results might be an underestimation of the variability in practice across the UK and Ireland. This multi-institutional study sheds light on controversial aspects in the management of phyllodes tumours and breast sarcoma, identifies the need for national guidelines to inform best practice, and calls for the centralisation of the management of breast sarcoma within specialist centres.