Integrating single-cell and spatial transcriptomes reveals COL4A1/2 facilitates the spatial organisation of stromal cells differentiation in breast phyllodes tumours

BACKGROUND

Breast phyllodes tumours (PTs) are a unique type of fibroepithelial neoplasms with metastatic potential and recurrence tendency. However, the precise nature of heterogeneity in breast PTs remains poorly understood. This study aimed to elucidate the cell subpopulations composition and spatial structure and investigate diagnostic markers in the pathogenesis of PTs.

METHODS

We applied single-cell RNA sequencing and spatial transcriptomes on tumours and adjacent normal tissues for integration analysis. Immunofluorescence experiments were conducted to verify the tissue distribution of cells. Tumour cells from patients with PTs were cultured to validate the function of genes. To validate the heterogeneity, the epithelial and stromal components of tumour tissues were separated using laser capture microdissection, and microproteomics data were obtained using data-independent acquisition mass spectrometry. The diagnostic value of genes was assessed using immunohistochemistry staining.

RESULTS

Tumour stromal cells harboured seven subpopulations. Among them, a population of widely distributed cancer-associated fibroblast-like stroma cells exhibited strong communications with epithelial progenitors which underwent a mesenchymal transition. We identified two stromal subpopulations sharing epithelial progenitors and mesenchymal markers. They were inferred to further differentiate into transcriptionally active stromal subpopulations continuously expressing COL4A1/2. The binding of COL4A1/2 with ITGA1/B1 facilitated a growth pattern from the stroma towards the surrounding glands. Furthermore, we found consistent transcriptional changes between intratumoural heterogeneity and inter-patient heterogeneity by performing microproteomics studies on 30 samples from 11 PTs. The immunohistochemical assessment of 97 independent cohorts identified that COL4A1/2 and CSRP1 could aid in accurate diagnosis and grading.

CONCLUSIONS

Our study demonstrates that COL4A1/2 shapes the spatial structure of stromal cell differentiation and has important clinical implications for accurate diagnosis of breast PTs.

Surgical Management and System Therapy of the Most Giant Known Malignant Metastatic Breast Phyllodes Tumor: A Case Report and Review of the Literature

INTRODUCTION

Phyllodes tumors belong to uncommon fibroepithelial breast tumors with a range of biological behaviors. Phyllodes tumors are responsible for less than 1 percent of all neoplasms of the breast.

CASE PRESENTATION

A 66-year-old woman presented to our Breastcancer Unit in March 2021 because of a huge mass of her left breast with bleeding out of a tumor necrosis. Five years ago in 2016, a benign phyllodes tumor was diagnosed externally. When we started the treatment, the tumor had a weight of 18.6 kg.

CONCLUSION

We describe the surgical management and the systemic treatment of metastatic disease.

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.

Fibroepithelial tumours of the breast-a review

Fibroepithelial tumours of the breast are biphasic neoplasms composed of both epithelial and stromal elements, including the common fibroadenoma and the infrequent phyllodes tumour. The admixture of epithelium and stroma in the fibroadenoma shows intra- and pericanalicular patterns, and may display a variety of histological changes. Fibroadenoma variants include the cellular, juvenile, myxoid and complex forms. The cellular fibroadenoma may be difficult to distinguish from the benign phyllodes tumour. Stromal mitotic activity can be increased in fibroadenomas in the young and pregnant patients. Phyllodes tumours, neoplasms with the potential for recurrence, show an exaggerated intracanalicular growth pattern with broad stromal fronded architecture and stromal hypercellularity. They are graded into benign, borderline and malignant forms based on histological assessment of stromal features of hypercellularity, atypia, mitotic activity, overgrowth and the nature of the tumour borders. Classification of phyllodes tumours is imperfect, compounded by tumour heterogeneity with overlapping microscopic features among the different grades, especially in the borderline category. Malignant phyllodes tumours can metastasise and cause death. Determining which phyllodes tumours may behave aggressively has been difficult. The discovery of MED12 mutations in the pathogenesis of fibroepithelial tumours, together with other gene abnormalities in the progression pathway, has allowed refinements in diagnosis and prognosis.

Case report: Transformation of juvenile fibroadenoma to borderline phyllodes tumor in young lady

Introduction

Fibroadenoma is the most common benign tumor found in young women. Transformation for Fibroadenoma to borderline phyllodes tumor is rare. Phyllodes tumor tends to recur locally due to the aggressive nature of the phyllodes tumor tissue, which tends to become malignant when recurrence occurs.

Presentation of case

We report an 18-year-old woman with a lump in the right breast for one year, a mass in the upper lateral quadrant measuring 20x15x10cm; the lump felt mobile, supple, cystic. 2 years earlier, lumpectomy surgery with anatomical pathology of fibroadenoma mammae with 6 cm. A biopsy was performed, the result was a borderline phyllodes tumor. Neoadjuvant chemotherapy was performed with tumor reduction >50%, followed by wide excision surgery with tumor-free margins. The first one-year evaluation showed no signs of recurrence, and no signs of distant metastases were found.

Conclusion

Our patient had a juvenile relapse FA which progressively changed to borderline tumor phyllodes borderline. We report this case to the need for continuous follow-up for fibroadenoma cases and the possibility of recurrence and becoming malignant.

Fibroepithelial lesions revisited: implications for diagnosis and management

Fibroepithelial lesions of the breast, comprising the fibroadenoma and phyllodes tumour, are a unique group of neoplasms that share histological characteristics but possess different clinical behaviour. The fibroadenoma is the commonest benign breast tumour in women, while the phyllodes tumour is rare and may be associated with recurrences, grade progression and even metastasis. The diagnosis of fibroadenoma is usually straightforward, with recognised histological variants such as the cellular, complex, juvenile and myxoid forms. The phyllodes tumour comprises benign, borderline and malignant varieties, graded using a constellation of histological parameters based on stromal characteristics of hypercellularity, atypia, mitoses, overgrowth and the nature of tumour borders. While phyllodes tumour grade correlates with clinical behaviour, interobserver variability in assessing multiple parameters that are potentially of different biological weightage leads to significant challenges in accurate grade determination and consequently therapy. Differential diagnostic considerations along the spectrum of fibroepithelial tumours can be problematic in routine practice. Recent discoveries of the molecular underpinnings of these tumours may have diagnostic, prognostic and therapeutic implications.