Metastatic breast cancer masquerading as gastrointestinal primary.

Seven patients with metastatic breast cancer presenting as gastrointestinal primary are described. These included six gastric and one colonic lesions. None of the patients had known systemic metastases at the time of diagnosis. The mean age at presentation was 66.7 yr (range 55-78). Median interval between breast cancer and gastrointestinal metastasis diagnosis was 6 yr (range 0.25-12.5). Original breast cancer histology included infiltrating lobular cancer (n = 4), infiltrating ductal cancer (n = 1), and a mixed type (n = 2). All patients with gastric involvement presented with epigastric pain and early satiety; the patient with colonic involvement had heme-positive stool. In three cases of gastric tumor and the one case of colonic tumor presentation, a definitive diagnosis of metastatic breast cancer was only confirmed after surgical resection of a presumed primary gastric or colonic malignancy. In the other three cases, pathological diagnostic confirmation was obtained through endoscopic biopsies and comparison to breast biopsy material, and operative treatment was avoided in favor of systemic cytotoxic therapy. The diagnosis was confirmed through similarities between mammary and gastric histopathology with regard to growth pattern, hormone receptor status, or gross cystic disease fluid protein. A high level of suspicion for metastatic breast cancer and a detailed pathological analysis will help avoid unnecessary surgical treatment in patients with a history of mammary carcinoma presenting with a newly diagnosed gastrointestinal neoplasm.