Case report

A 56-year-old woman from Saposoa, San Martín, Peru, was referred to the surgical oncology service for evaluation of a rapidly enlarging left breast mass with a 1-year history of progressive growth. Physical examination revealed a multinodular mass measuring 25 × 20 cm, involving all breast quadrants and displaying a reddish-purple appearance. The nipple–areolar complex was preserved, and a 1.2-cm ipsilateral axillary lymph node was palpable. The patient denied a family history of breast cancer or PT. She also had mild intellectual disability, resulting in communication and functional limitations.

Breast ultrasound demonstrated a heterogeneous hypoechoic mass with lobulated margins, measuring 120 × 69 mm, containing focal necrotic areas and increased vascularity, along with reactive axillary lymph nodes. Chest computed tomography revealed a 126 × 142 × 103 mm left breast tumor with lobulated irregular borders, central necrosis, peripheral contrast enhancement, and prominent neovascularization. The lesion infiltrated the nipple–areolar complex and was closely related to the pectoralis major and adjacent intercostal muscles (Fig. 1).

Figure 1: The radiological and macroscopic findings of the tumor; computed tomography revealed a large left breast mass with lobulated and irregular margins, areas of central necrosis, neovascularization, and probable involvement of the adjacent muscle layer; likewise, the clinical and surgical specimen images demonstrate the enormous size of the lesion and the significant local involvement caused by tumor growth.

Core needle biopsy showed a fibroepithelial neoplasm with increased stromal cellularity, marked atypia, necrosis, and a mitotic count >10/10 high-power fields, raising suspicion of malignant PT (Table 1). A left total mastectomy was performed. Histopathological examination confirmed a 15-cm malignant PT characterized by marked stromal cellularity and atypia, stromal overgrowth, skin infiltration by direct extension, mitotic activity >10/10 high-power fields, absence of heterologous elements, and negative surgical margins (Fig. 3A–C).

Feature | Benign | Borderline | Malignant
Stromal cellularity | Low | Moderate | High
Nuclear atypia | Absent or mild | Moderate | Marked
Mitotic index | <5 mitoses per 10 high-power fields | 5–9 mitoses per 10 fields | ≥10 mitoses per 10 fields
Tumor margins | Well-defined | They can be infiltrative | Generally infiltrative
Metastatic potential | Absent | Low | High, mainly hematogenous

The surgical specimen weighed 1.526 kg and measured 25 × 20 × 12 cm, containing a solid mass measuring 15 × 11.5 × 9 cm involving all breast quadrants and the retroareolar region (Fig. 2). Owing to the extensive defect after resection, primary closure was not feasible, leaving a 12 × 6 cm central defect. Following intraoperative margin widening, a split-thickness skin graft was placed 10 days later after adequate granulation tissue formation. At 7-day follow-up, the graft remained viable with satisfactory integration and coloration (Fig. 4).

Figure 2: The characteristic microscopic findings of the PT, highlighting the progressive increase in stromal cellularity, the presence of nuclear atypia, and the typical cleft or “leaf” configuration, findings that led to the diagnosis of a fibroepithelial neoplasm with aggressive biological behavior.

Figure 3: The histopathological criteria for malignancy observed in the surgical specimen, including infiltrative margins, areas of tumor necrosis, marked stromal hypercellularity, nuclear pleomorphism, and high mitotic activity; these findings confirmed the definitive diagnosis of malignant PT.

Figure 4: The postoperative evolution after total mastectomy and reconstruction using a partial-thickness skin graft; adequate graft integration, satisfactory coverage of the surgical defect, and absence of evident local complications during follow-up are observed.