Paget disease of the breast with underlying invasive ductal cancer in neurofibromatosis type 1: a case report.

Background: Neurofibromatoses (NFs) are a group of rare autosomal dominant genetic disorders characterized by tumors growing in the nervous system. Neurofibromas, which are soft noncancerous tumors, have been found on or under the skin in patients with NF1. Furthermore, patients with NF1 are susceptible to various cancers, including breast cancer. Neurofibromas under the skin of the breast can delay the diagnosis of breast cancer, which severely reduces life expectancy. Paget disease of the breast (PDB) is a rare type of breast cancer that causes eczema-like changes of the nipple. Case Description: Here, we present a rare case of a 50-year-old woman who was diagnosed with NF1 and an invasive ductal breast carcinoma accompanied by PDB. The patient underwent mastectomy, sentinel lymph node biopsy, and adjuvant therapies, including chemotherapy, anti-human epidermal growth factor receptor 2 (HER2) therapy, and endocrine therapy. No local recurrence or distance metastasis was found at 3 years of follow-up. Conclusions: NF1 patients aged <50 years have a higher risk of breast cancer and a worse prognosis. Moreover, neurofibroma in the breast can easily mask signs of breast cancers. Therefore, early breast cancer screening is crucial for patients with NF1. Radiotherapy should be avoided because of potential carcinogenicity to the neurofibromas. Mastectomy, and not breast-conserving surgery, is the optimal choice. Patients should undergo regular postoperative follow-up so that contralateral breast cancer can be detected early.