Right Stage IIB ER/PR-positive breast cancer with left epithelioid MPNST: no recurrence after surgery

What happened, in summary

This 76-year-old woman came to the hospital after noticing enlarging masses in both breasts over the previous year. She had no family history of breast, ovarian, pancreatic, or prostate cancer and no signs suggesting neurofibromatosis, such as café-au-lait spots, Lisch nodules, or cutaneous neurofibromas. On examination, the right breast mass measured 40 mm and the left breast mass measured 80 mm. Mammography, ultrasound, and breast MRI showed suspicious findings in both breasts. Biopsy of the right breast showed invasive ductal carcinoma that was strongly hormone receptor-positive, with ER Allred score 8 and PR Allred score 8, HER2 1+ / HER2-negative status, and Ki-67 of 7%. Biopsy of the left breast showed a mesenchymal tumor. She underwent right total mastectomy with sentinel lymph node biopsy and left total mastectomy. Final pathology showed 2 different tumors. The right breast had a 50 × 42 × 60 mm invasive ductal carcinoma, solid type, staged pT3N0M0, Stage IIB. The left breast had a 75 × 70 × 60 mm epithelioid malignant peripheral nerve sheath tumor with spindle cells, epithelial-like cells, and mild invasion of surrounding mammary tissue. Immunohistochemistry for the left tumor was positive for vimentin, S100, and SOX10, with partial cytokeratin AE1/AE3 positivity and maintained H3K27me3 expression. That tumor was staged pT2, Stage IIIA, histological malignancy grade 2. After surgery, she received oral anastrozole as endocrine therapy for the right breast cancer. No adjuvant therapy was given for the left epithelioid malignant peripheral nerve sheath tumor. As of March 2025, 3 years after surgery, neither tumor had recurred.