Metastatic gastric adenocarcinoma primarily presenting in the fallopian tube

We report a 48-year-old woman presenting with gastric adenocarcinoma metastatic only to the left fallopian tube. In addition to invasive, poorly differentiated adenocarcinoma, there were areas simulating intraepithelial carcinoma, suggesting a primary fallopian tube lesion. The differential diagnosis included a metastatic process, based on unusual morphologic patterns with occasional signet-ring cells, single-cell linear pattern of infiltration, and abundant lymphvascular space invasion. Metastasis from an upper gastrointestinal primary was confirmed by immunostains (cytokeratin 7, CDX-2, and p53 positive in the tumor cells and cytokeratin 20, WT-1, estrogen, and progesterone receptors negative). Imaging studies and a posterior biopsy demonstrated primary gastric adenocarcinoma with similar histology and immunoprofile. We report an unusual case of primary gastric adenocarcinoma presenting only in the fallopian tube and discuss its mimics and differential diagnosis.