Cutaneous metastases from breast carcinoma: calretinin expression and estrogen, progesterone and Her2/neu status of the metastases, compared to primary cutaneous apocrine tumors.

Recently, it has been demonstrated how apocrine glands, as well as several cutaneous apocrine tumors, do not express calretinin. In the current report, we studied calretinin immunoexpression in 33 cases of cutaneous metastases of ductal breast carcinoma, as well as in seven primary cutaneous apocrine tumors. We also tested the hormonal status of all cases for estrogen receptors (ER), progesterone receptors (PR), and ERRB2. From the 33 metastases, 26 (78.79%) cases were calretinin-negative and seven cases expressed the marker. Five (15.15%) cases were triple-negative (ER-, PR-, Herceptest-). Of these five cases, three cases were calretinin+ and two cases were calretinin-. Three out of the seven cases that expressed calretinin were triple-negative. From the seven primary cutaneous apocrine tumors, only one showed focal expression of calretinin, and six of them showed a triple-negative immunophenotype. Only the ER+, PR+ case showed morphologic features on an "in situ" apocrine carcinoma. We concluded that our findings support the value of calretinin in the differential diagnosis between a metastasis from breast carcinoma into the skin and a primary cutaneous apocrine carcinoma (CAC), especially in triple-negative cases. However, hormonal markers plus calretinin would not be sufficient to discriminate between both diagnostic possibilities, and they are probably better used when integrated in a wide immunohistochemical panel.