E-cadherin immunohistochemical analysis of histiocytoid carcinoma of the breast.

Histiocytoid carcinoma is a rare type of invasive breast carcinoma. It has been considered to be a variant of lobular carcinoma, a variant of apocrine ductal carcinoma, and an apocrine variant of lobular carcinoma and to resemble lipid-rich carcinoma. In attempts to elucidate its histogenesis, investigators have used mucin and oil red O histochemical analysis and GCDFP-15 immunostaining. E-cadherin is a relatively recent addition to the armamentarium of immunohistochemical markers used for cell differentiation and is a member of a family of transmembrane glycoproteins that has been shown to have a strong correlation with the histologic phenotypes of breast carcinoma. Most ductal carcinomas show diffuse membrane expression of E-cadherin, and lobular carcinomas are characterized by complete lack of membrane staining of E-cadherin. The object of this study was to use E-cadherin immunohistochemical analysis to help clarify the histogenesis of histiocytoid carcinoma. Fourteen cases containing the diagnosis of histiocytoid carcinoma of the breast were identified at M. D. Anderson Cancer Center (Houston, TX) from 1988 to 2001. All cases were rereviewed, histologic features were evaluated, and immunohistochemical staining with E-cadherin and GCDFP-15 was performed. Clinical information was extracted from the patients' medical records. Eleven cases met published histologic criteria for histiocytoid carcinoma. The remaining three cases were apocrine carcinoma. The pattern of tumor infiltration was solid, without secondary lumen formation in all cases of histiocytoid carcinoma. Lobular carcinoma in situ was identified in eight cases, but was absent in three. There was no E-cadherin immunohistochemical staining in eight of the 11 cases of histiocytoid carcinoma (72.7%). GCDFP-15 was immunoreactive in all 10 cases of histiocytoid carcinoma where it was performed. Follow-up data was available for nine of the 11 cases of histiocytoid carcinoma: six patients were alive with disease at 1.5 to 48 months, one patient had died of disease at 60 months, and two patients had no evidence of disease at 32 and 45 months. We conclude that histiocytoid carcinoma has an immunophenotypical profile consistent with both ductal and lobular differentiation. Moreover, the lack of consistent morphologic features, a specific clinical profile, and a distinct immunohistochemical pattern lead us to hypothesize that histiocytoid carcinoma is not a special type of breast cancer. Copyright 2002, Elsevier Science (USA). All rights reserved.