Breast cancer is the most frequently seen cancer in females but primary neuroendocrine carcinoma of the breast, which was defined as a separate entity in the 2003 World Health Organisation tumour classification, is seen extremely rarely. This entity, which is still not well-defined and has not been well-researched, demonstrates a more aggressive course than invasive ductal carcinoma. As metastatic breast neuroendocrine tumours are more widespread and the treatment strategy is different, preoperative differential diagnosis is important. The basic diagnostic method is pathological examination. If a neuroendocrine pattern is determined in microscopy, then immunohistochemical study of neuroendocrine markers should be made. It is necessary to be vigilant in terms of synchronous tumours and metachronous tumours which may develop in the postoperative period as the incidence of synchronous and metachronous cancers in patients with neuroendocrine tumours is higher compared to the general population. The case presented here is of a 73-year old patient who presented with complaints of a breast lump, which was thought to be invasive breast cancer, and as a result of the operation with pathological and immunohistochemical examination, primary neuroendocrine carcinoma of the breast was determined. With more advanced evaluations, no synchronous or metachronous tumours were determined.