Efficacy of neoadjuvant endocrine therapy in patients with poorly differentiated neuroendocrine carcinoma of the breast: A case report

RATIONALE: Poorly differentiated neuroendocrine carcinoma of the breast is a rare cancer with poor prognosis. There is no standard treatment for the disease. Neoadjuvant therapies and surgery are considered to be the main treatment when the tumor diameter is greater than 5.0 cm. Neoadjuvant therapies include chemotherapy and endocrine therapy. However, the effect of neoadjuvant endocrine therapy is not clear in the disease. PATIENT CONCERNS: In August 2014, a 28-year-old premenopausal woman noted a mass that was approximately 3.0 cm∗2.0 cm in size on her right breast with pain. Subsequently, the mass has been always increasing significantly. In August 2015, the mass was approximately 7.0 cm∗5.0 cm in size, accompanied by pain, no nipple retraction and discharge, no orange peel-like skin changes, and no dimples. In addition, she had no salient past history. DIAGNOSES: Histopathological examinations by a biopsy with a thick needle (hollow needle) and surgical resection confirmed poorly differentiated neuroendocrine carcinoma of the right breast. INTERVENTIONS: First and remarkably, she underwent 3 months of neoadjuvant endocrine therapy (goserelin once every 28 days, and letrozole 10 mg every day). Then, she underwent surgery - stage I breast reconstruction by using prosthesis. Adjuvant endocrine therapy has been used since the operation. OUTCOMES: According to response evaluation criteria in solid tumors 1.1, the tumor was shrunk by 78.87% after neoadjuvant endocrine therapy. No salient complications were observed. We have followed her for 48 months, and there are no signs of recurrence and metastasis. LESSONS: Poorly differentiated neuroendocrine carcinoma of the breast is rare and has a poor prognosis. Currently, there is no standard treatment for this disease. Studies show estrogen receptor and progesterone receptor of neuroendocrine carcinoma of the breast are often highly expressed. In the case, it can be observed that estrogen receptor and progesterone receptor are highly expressed. Therefore, neoadjuvant endocrine therapy may be considered in neuroendocrine carcinoma of the breast when the mass is large and the patient refuses neoadjuvant chemotherapy. We hope to provide an attractive evidence for neoadjuvant endocrine therapy of neuroendocrine carcinoma of the breast. However, more cases are still being needed for research.