Expression of oestrogen receptor and loss of E-cadherin are diagnostic for gastric metastasis of breast carcinoma

Aims: To investigate whether immunohistochemical staining for oestrogen receptor (ER)α, progesterone receptor (PgR) and E-cadherin might be useful to differentiate between metastatic breast carcinoma and primary gastric carcinoma. Methods: Gastric biopsies of 75 patients containing adenocarcinoma were stained for ERα, PgR and E-cadherin. Included were: Group A, 28 patients with primary gastric cancer; Group B, 28 patients with an adenocarcinoma containing gastric biopsy and a clinical diagnosis of metastatic breast carcinoma; Group C, all consecutive patients with a positive gastric biopsy in 2001 (n = 19) without clinical history of breast carcinoma and not followed by gastric resection (control group). Results: All ERα+ or PgR+ carcinomas (n = 20) were of patients with a previous or concurrent history of breast carcinoma: 19 in group B, one in group C. In addition, absence of E-cadherin staining was seen significantly more often in patients with metastatic breast carcinoma than in patients with primary gastric cancer (P < 0.001). Conclusion: Positive immunohistochemical staining for ERα or PgR of an adenocarcinoma in a gastric biopsy is diagnostic for metastatic breast carcinoma. Moreover, when carcinoma in a gastric biopsy is negative for E-cadherin staining, metastatic breast carcinoma should be considered.