Synchronous Invasive Ductal Carcinoma with Neuroendocrine Features and Metastatic Gastrointestinal Neuroendocrine Tumor: A Rare Case Report

We report a rare case of a 58-year-old African-American woman who presented with abdominal pain and was found to have a well-differentiated gastrointestinal neuroendocrine tumor (NET) metastatic to the liver. During her workup, a left breast mass was detected. Core biopsy of the breast lesion revealed invasive ductal carcinoma (IDC) with neuroendocrine differentiation (ER-positive, PR-negative, HER2-negative). ^68Ga-DOTATATE PET/CT confirmed somatostatin receptor–positive lesions in the liver, bone, and mesentery, consistent with metastatic NET, but did not show additional uptake in the breast. The patient underwent partial mastectomy of the breast mass and subsequently received peptide receptor radionuclide therapy (PRRT) with ^177Lu-DOTATATE for her metastatic NET. This case illustrates an unprecedented synchronous presentation of primary IDC with neuroendocrine features together with a metastatic gastrointestinal NET within the same breast, highlighting the diagnostic challenge and the utility of ^68Ga PET/CT imaging and PRRT in management.