Differential sensitivity of estrogen/progesterone receptors and BRST-2 markers in metastatic ductal and lobular breast carcinoma to the skin.

Cutaneous metastases arising from breast carcinoma are quite common. A standard panel of immunohistochemical markers including estrogen receptor (ER), progesterone receptor (PR), and BRST-2 are frequently used in surgical pathology to identify neoplasms with breast differentiation. It is well known that as the grade of a tumor increases, and as tumors lose their differentiation, immunohistochemistry results become more unpredictable in determining possible primary sites of origin. Although previous studies have identified a decrease of ER sensitivity in breast metastases, a possible sensitivity differential of cutaneous metastases of invasive lobular versus invasive ductal carcinoma by using the standard immunohistochemical panel has not been previously reported. With the standard panel, we compared the staining sensitivity of metastatic invasive ductal carcinoma (10 cases) to metastatic invasive lobular carcinoma (four cases) to the skin. ER positivity was identified in one case of metastatic ductal carcinoma and none of the four lobular carcinomas. PR positivity was noted in all cases of metastatic ductal and lobular carcinoma. BRST-2 positivity was found in only two of 10 cases of metastatic ductal carcinoma and all four of four cases of metastatic lobular carcinoma. These results indicate that a differential sensitivity exists for the BRST-2 marker when comparing cutaneous metastases of invasive lobular with invasive ductal carcinoma.