Duodenal metastasis of breast invasive carcinoma of no special type: a rare presentation

The authors read with attention the case report by Vande Berg and coworkers, published on a previous issue of this journal, describing a rare diagnosis of rectal metastases of an incognito invasive lobular breast carcinoma (ILC), for which immunohistochemistry was decisive (1). Likewise, we share a similarly rare case of gastrointestinal metastases of breast carcinoma (BC), in which immunohistochemistry played a pivotal role.A 55-year-old woman was diagnosed in June 2015 with an Invasive Breast Carcinoma of no-special-type (IBCNST) grade III, human epidermal growth factor receptor 2 (HER2) positive, estrogen and progesterone receptors (ER/PR) negative. Biopsy revealed vascular permeation. Neoadjuvant chemotherapy and trastuzumab preceded surgery, performed in December 2015, followed by radiotherapy and trastuzumab. The patient remained free of disease until 2017, when a right cerebellar lesion was diagnosed as BC metastasis and was treated with stereotactic radiosurgery. In January 2020, the patient presented with a 1-month history of post-prandial vomiting, epigastric pain, anorexia, fatigue, and a 10 kg weight loss. Lab tests were unremarkable, except for small increase in CA-125 and CA-15.3.