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.