Primary Neuroendocrine Tumors of the Breast According to the WHO 2019 Classification;Real Life Experiences of Rare Tumor Types of the Breast.

Backround: Neuroendocrine neoplasms (NEN) originate in many body parts, with 70% reported from the gastrointestinal system, 25% from the lungs. NENs of the breast account for <1% of all NENs. The primary breast NEN nomenclature was changed in the most recent World Health Organization(WHO) classification in 2019. Since the pathological classification has changed several times, there are no definitive data on treatment management.

Methods: In this study, patients followed up in our clinic were pathologically re-evaluated according to the latest classification.

Results: The clinical characteristics, treatments, recurrence and survival status of 36 patients with early-stage primary breast NEN were examined. A statistically significant difference was determined in respect of overall survival (OS) for the Eastern Cooperative Oncology Group Performance Score (ECOG PS), type of surgery, age ≥ 70 years, PR positivity and tumor size. A low ECOG PS, younger age, breast-conserving surgery, and small tumor diameter were associated with better survival. A low ECOG PS, early stage, breast-conserving surgery, and fewer than four malignant lymph nodes were associated with better disease-free survival (DFS). All the patients in this study were at an early stage and were treated for typical breast cancer, although some patients diagnosed with neuroendocrine carcinoma (NEC) received cisplatin and etoposide treatment.

Conclusion: In our study; the prognosis of breast NEN patients was better than the literature data. Maybe the prognosis of patients evaluated as breast NEN according to the new classification is better than the older classification groups.