Breast tumor with giant borderline phyllodes: Case report and literature review.

Rationale: Giant phyllodes tumors are rare fibroepithelial neoplasms, accounting for less than 1% of all primary breast tumors. Their main features are a single-round mass, progressive enlargement, and a high rate of local recurrence. A phyllodes tumor measuring more than 10 cm in diameter is usually defined as a "giant" tumor. Surgery remains the primary treatment option, although the efficacy of adjuvant radiotherapy needs to be confirmed by further studies.

Patient concerns: We report a rare case involving a 38-year-old woman who presented, in May 2022, with a large, borderline lobulated tumor in her left breast, measuring 35 cm × 30 cm. She needed to physically support the mass when performing any activity, and even slight physical activity elevated her heart rate to 130 beats/min. In addition, the patient was unable to lie flat and could only sleep on her left side.

Diagnoses: Breast B-ultrasound examination and chest computed tomography scans showed the possibility of inflammatory changes. Ultrasound-guided pathologic examination of the mass could not determine the type of mass. Immunofluorescence and bacterial culture of the aspirated fluid were also negative, ruling out the possibility of infection. A mastectomy was then performed to clarify the diagnosis.

Interventions: The tumor was completely removed, and the patient did not receive any adjuvant therapy after surgery.

Outcomes: The patient recovered smoothly. Unfortunately, she experienced a recurrence of the left breast mass six months later, which progressed to malignancy.

Lessons: The most effective treatment for phyllodes tumors of breast is wide local excision with clean margins greater than 1 cm. Simple mastectomy is recommended for borderline or malignant cases, especially when it is difficult to achieve reliable negative margins. Although adjuvant radiotherapy and chemotherapy after surgery are not generally recommended as first-line treatments, it raises the question of whether the recurrence could have been delayed if the patient had received postoperative radiation therapy.