Discovery of a neuroendocrine tumor of the caecum by mammary metastasis using 18F-DOPA-PET.

Neuroendocrine tumors (NET) develop from the diffuse endocrine system. These are rare tumors that can affect diverse organs. We present here the case of a 42-year-old female patient in whom a NET of the breast was discovered that was likely not of mammary origin. The main challenge was finding the primary tumor using immunohistochemistry and specific medical imaging modalities for NET. The primary tumor was localized at the last ileal loop upstream of the Bauhin valve thanks to the use of 18F-DOPA-PET. Ileocaecal resection by laparoscopy was performed. A WHO grade 2 NET of the ileum measuring 2.2 cm × 1.5 cm was found that infiltrated the submucosa with six metastatic lymph nodes of the eight removed (6N+/8). This unusual clinical case is the first one of a digestive NET of the ileum-caecal junction by mammary metastasis.