International Journal of Case Reports and Images (IJCRI) is an international, peer reviewed, monthly, open access, online journal, publishing high-quality, articles in all areas of basic medical sciences and clinical specialties.Aim of IJCRI is to encourage the publication of new information by providing a platform for reporting of unique, unusual and rare cases which enhance understanding of disease process, its diagnosis, management and clinico-pathologic correlations.IJCRI publishes Review Articles, Case Series, Case Reports, Case in Images, Clinical Images and Letters to Editor. Website: www.ijcasereportsandimages.comNeuroendocrine tumor of the breast:Is it primary or metastatic?Ornela A. Dervishaj, Alexandra S. Renzi, Romulo Genato, Philip Q. Xiao, Armand P. Asarian ABSTRACT Introduction: Neuroendocrine breast carcinoma is a rare form of tumor that may be either primary or metastatic. Case Report: We present the case of a patient who was referred to our outpatient office with the diagnosis of a triple negative invasive breast carcinoma on an ultrasound-guided core needle biopsy. The patient subsequently underwent a lumpectomy with sentinel lymph node biopsy. Postoperative pathology revealed neuroendocrine carcinoma of the breast with sentinel lymph node biopsy negative for carcinoma. The tumor cells were positive for AE1/AE3, chromogranin, synaptophysin and CD-56 but negative for estrogen, progesterone and HER2. To exclude a primary carcinoma elsewhere, we obtained a whole body PET scan which showed a mildly hypermetabolic mesenteric mass in the midline with curvilinear calcification. Computed tomography scan of the abdomen and pelvis with oral and IV contrast showed a mass-like soft tissue within the terminal ileum with thickening of the cecum. An octreotide scan of the whole body revealed abnormal activity in the midline of the lower abdomen 6 hours and 24 hours after administration of octreotide. Colonoscopy showed a nodular friable mass in the ileocecal valve extending from the terminal ileum. Biopsy from the colonoscopy demonstrated a neuroendocrine carcinoma. The patient subsequently underwent a right hemicolectomy with primary anastomosis. Postoperative pathology was concordant with a neuroendocrine carcinoma and 9 of the 20 lymph nodes were positive for carcinoma. We performed a literature review to explore the reported incidence, diagnosis and treatment of this rare tumor metastasizing to the breast. Conclusion: Differentiating between primary and metastatic tumor of the breast represents a challenge, albeit an important one, as the first disease can subject the patient to the morbidities of a mastectomy with axillary node dissection and the other is locally controlled.