Malignant Phyllodes Tumor of the Breast: Case Report

Introduction : Phyllodes tumors (PT) are rare and account for 0.3% to 0.5% of all breast tumors. PT may be classified as benign, borderline or malignant. The aim of this study was to report a case of malignant PT of the breast. Case report : A 27-year-old woman presented with a mass in the left breast with histopathological features of malignancy (results of US of the breast: an oval, lobulated hypoechogenic lesion, measuring 7.7 cm – BI-RADS® 4C). A segmental resection (SR) of the breast was performed and histopathology study of the surgical specimen confirmed a malignant PT. Adjuvant radiotherapy was used for supplemental treatment. One year later, the patient had a local recurrence of the primary tumor and underwent a new SR of the left breast. There was no indication of breast reirradiation. At about 31 months after diagnosis (September 2019 – April 2022), the patient is well and adherent to periodical clinical follow-up. Conclusion : This study presents a case of malignant PT that occurred in a young patient and had a more aggressive course.


INTRODUCTION
Phyllodes tumor (PT) is a rare breast neoplasm. The incidence of PT is 0.3-0.5% of all breast tumors, occurring most commonly in women aged 35 to 65. PT has a benign origin in around 85-90% of the cases 1 . They are classically divided into benign, borderline or malignant 2 . Patients with PT usually present a fast-growing palpable mass with features similar to fibroadenoma on ultrasonography (US) 3 . Local recurrence of malignant PT is approximately 19-40%, and the mean period of recurrence is 1-39 months (mean: 20.3 months). The risk of distant metastases is higher than 75% in the first 120 months, meaning a worse prognosis 4 .
The treatment of choice for these tumors is segmental resection (SR) of the breast with adequate margins 1 . Adjuvant radiotherapy is also indicated following SR in cases of borderline or malignant tumors larger than 5.0 cm and/or involved margins 2 . Adjuvant radiotherapy has been shown to increase disease-free survival in these cases. However, available data on increased overall survival in the literature remain inconclusive 3 . The aim of this study was to report a case of malignant PT of the breast.
The Institutional Review Board of "Universidade Estadual do Piauí", Teresina (PI), Brazil -reference number 5.137.868 approved the study. The patient signed the informed consent form (ICF).

CASE REPORT
A 27-year-old woman sought medical attention in April 2019 presenting with a lump in the left upper outer quadrant (LUOQ) of the left breast -measuring 9 cm on physical examination. US of the breast revealed an oval, lobulated hypoechogenic lesion, measuring 7.7 cm (BI-RADS® 4C). Core needle biopsy and histopathological study demonstrated a lesion with spindle cell proliferation and discrete atypia. Further investigation of the surgical specimen was indicated and SR of the breast was performed in August 2019 (Figure 1).
In September 2019, histopathology study of the surgical specimen ( Figure 2) showed a fibroepithelial tumor with the following features: areas of stromal expansion, spindle cell proliferation, atypias and frequent mitotic figures -with clear surgical margins. 5 months after initial symptoms, the definitive diagnosis was malignant PT. From February to April 2020, the patient underwent 3D adjuvant radiotherapy. The dose delivered was 50 Gy in 25 fractions to the left breast + boost of 10 Gy in 5 fractions to the LUOQ.
In September 2020, there was a recurrence of the primary tumor of the left breast (Figure 3), with detection

DISCUSSION
PT is a rare form of breast tumor. It accounts for about 2.5% of fibroepithelial tumors of the breast 2 , with an incidence of 2.1 per million women 3 . PT of the breast usually manifests as a painless rapidly growing unifocal mass that is most commonly located in the LUQ, as occurred in the case report 4 . The patient developed a malignant PT before 30 years of age, which is a major rare event.
The pathogenesis of PT is currently unclear. However, it is known that it is related to diverse factors, including hormone disorders (primarily hyperestrogenism), breast injury, ethnicity and breastfeeding. It may also occur during pregnancy 1,4 . Histologically, PT is characterized by a double-layered leaf-like epithelial pattern with hypercellular stroma 2 .
The treatment of choice for these cases is SR with a 1.0 cm margin and without axillary node dissection [1][2][3][4][5] . According to a systematic review with meta-analysis conducted by Toussaint et al., the width of the safety margin is related to lower local recurrence, mainly in malignant PT, although a significant difference in the occurrence of metastases was not found 6 . In the present case, the primary tumor was treated with SR and left breast irradiation. However, about one year later, there was a local recurrence with repeated SR.
Radiotherapy has been shown to be effective at preventing local recurrence, in addition to increasing functioning of the area and patient satisfaction 2 . In general, 45-50 Gy is delivered to subclinical lesions 1 . For this patient, a dose 50 Gy in 25 fractions to the primary tumor of the left breast + boost of 10 Gy in 5 fractions to the LUOQ were used. Left breast reirradiation was not indicated.
Due to limited data on chemotherapy for PT of the breast, systemic chemotherapy is not indicated in these cases, except in non-resectable distant metastases (uncommon event) 7,8 . This modality of treatment was not indicated for this patient.
At about 31 months after diagnosis, the patient is in good clinical condition and adheres to periodical clinical follow-up in the medical unit.

CONCLUSION
This study presents a case of malignant PT that occurred in a young patient and had a more aggressive course.

CONTRIBUTIONS
Rafael Everton Assunção Ribeiro da Costa, and Luis Felipe Rodrigues Brandão de Barros: Study design, data acquisition, quality control of data, data analysis and interpretation, wording and review. Raimundo Gerônimo da Silva Júnior, Marcos Antonio Veras de Negreiros, Eid Gonçalves Coelho, Antonio Luiz Moreira Junior, and Carlos Eduardo Coelho de Sá: Study design, acquisition, quality control, analysis and interpretation of the data, wording, and critical review. All the authors approved the final version to be published.

DECLARATION OF CONFLICT OF INTERESTS
There is no conflict of interests to declare.

FUNDING SOURCES
None.