Triple-negative sebaceous carcinoma of the breast: no recurrence after multimodality treatment

What happened, in summary

This 33-year-old Brazilian woman had no family history of cancer and presented in December 2019 after feeling a right breast lump 2 months earlier. Ultrasound showed a solid irregular 2.4 × 1.4 cm nodule in the upper lateral quadrant, a second smaller nodule at the 4 o'clock position, and an enlarged right axillary lymph node. Core biopsy of the largest nodule showed Nottingham grade 3 invasive carcinoma with sebaceous differentiation. Immunohistochemistry showed a triple-negative phenotype, with estrogen receptor, progesterone receptor, and HER2 negativity, epithelial membrane antigen positivity, and Ki-67 of 50%. She first underwent quadrantectomy with sentinel lymph node biopsy. During surgery, another nodule that had not been seen on imaging was found near the 12 o'clock position and removed. Pathology confirmed grade 3 sebaceous carcinoma of the breast, a compromised superficial margin, and carcinoma metastasis in 1 axillary lymph node. The additional nodule showed invasive carcinoma of no special subtype with high-grade in situ disease and narrow margins, supporting multicentric disease; its profile was also triple-negative, with Ki-67 of 60% and features consistent with sebaceous carcinoma. One month later, she had right nipple-sparing mastectomy, axillary dissection, and prosthesis reconstruction. Margins were free, but residual sebaceous carcinoma was present. She then received weekly paclitaxel for 12 weeks, followed by dose-dense doxorubicin and cyclophosphamide every 21 days for 4 cycles. Adjuvant radiation to the right breast delivered 50.4 Gy in 28 fractions. Germline testing found no pathogenic or probably pathogenic variants. As of May 2025, after 5 years of follow-up with CT scans and mammography, there was no evidence of recurrence.