Triple-negative breast cancer developing beside a large breast cyst

What happened, in summary

A 67-year-old woman sought evaluation because a right breast cyst first seen 2 years earlier had progressively enlarged. Mammography showed a 7.2 cm mass, and ultrasound measured the complex solid and cystic lesion at 8.8 × 4.3 × 7.5 cm. Aspiration removed 50 mL of dark maroon fluid before biopsy of the solid component.

Core biopsy found poorly differentiated invasive ductal carcinoma, grade 3, together with high-grade ductal carcinoma in situ. The invasive cancer was estrogen-receptor negative, progesterone-receptor negative and HER2 negative, with Ki-67 above 50%. Clinically, the tumour was Stage II, and PET/CT showed no regional or distant metastases.

She completed 4 cycles of neoadjuvant carboplatin with weekly paclitaxel. Follow-up mammography and ultrasound showed the breast mass had decreased in size. She then chose breast-conserving surgery with a right partial mastectomy and sentinel lymph-node biopsy. Pathology showed residual poorly differentiated invasive ductal carcinoma measuring 1.8 × 1.6 × 1.0 cm with a small component of residual ductal carcinoma in situ. All 3 sentinel nodes were negative.

She recovered from treatment and had no clinical evidence of regional or distant recurrence at the latest follow-up described.