Immunohistochemical and genetic exploration of incompatible A blood group antigen expression in invasive micropapillary breast carcinoma: A case report.

INTRODUCTION: Invasive Micropapillary Carcinoma (IMPC) of the breast is a relatively rare subtype of invasive ductal carcinoma and represents the most inherently aggressive form. Expression of incompatible blood group A antigen in cancer of type O patients has been reported in several types of cancer, however, the biosynthetic mechanism and the genetic basis remain unclear until today. The aim of the present case report study was to evaluate the expression of incompatible blood group A antigen and to identify the genetic basis of this expression in IMPC of the breast.

MATERIAL AND METHODS: One patient blood group O with Invasive Micropapillary Carcinoma was screened at Pathology Department of University Hospital CHU Ibn Rochd, Casablanca. ABH antigens expression was assessed by immunohistochemistry. ABO genotyping was performed by allele specific primers PCR-ASP and Exon 6 of ABO gene was sequenced with Sanger method.

RESULTS: H antigen was expressed in endothelial and epithelial cells of normal tissue. However, H antigen expression was lost in both invasive micropapillary carcinomas. A antigen was expressed in IMPC with approximately 80% of positive cells. Tumor DNA was genotyped as heterozygous A/O. In normal DNA, we identified a single frameshift deletion c.320delA p.(Glu107Glyfs* 12), which is removed from tumor DNA.

CONCLUSION: Our findings suggest that incompatible A antigen expression in IMPC is due to glycosyltransferase A encoded by an A allele which is derived from O allele with a deletion at the position 320.