Cutaneous metastasis of signet-ring gastric adenocarcinoma to the breast with unusual clinicopathological features.

Background: Cutaneous metastasis of gastric adenocarcinoma is rare and usually presents in men, as nodules over the abdomen. We present the case of a woman with cutaneous metastasis of gastric adenocarcinoma showing unusual clinicopathological features.

Case Report: A 37-year-old woman developed florid cutaneous metastasis over the skin of the left breast two years after total gastrectomy for a signet-ring adenocarcinoma of the diffuse type. The metastasis presented as a multinodular growth developing over erythematous skin of the left hemithorax. Microscopically, the skin tumor was predominantly made up of spindle-shaped cells, mimicking a mesenchymal/fibrohistiocytic neoplasm. A comparative immunohistochemical study of the gastric primary and the skin tumor showed an almost identical profile (keratin 7/20+; epithelial membrane antigen+, MUC-5AC+), highlighting the gastric adenocarcinoma as the origin of the skin metastasis.

Conclusion: Although rare, cutaneous metastases of gastric adenocarcinomas can develop in women and may mimic inflammatory metastasis of breast adenocarcinoma. Immunohistochemistry is invaluable in establishing the correct diagnosis.