Photomicrographs showing male cells with X (red) and Y (green) chromosome signals within breast carcinoma after fluorescence in situ hybridization (FISH). (a,b) Male cells after FISH (arrows). Original magnifications: 630× for panel a and 1,000× for panel b. (c,d) A cluster of cytokeratin-positive cells: panel c shows male cells after FISH in a cluster of maternal cells (arrow), and panel d shows cytokeratin-positive male cell after FISH and immunolabelling (arrow). Original magnification: 1,000× for both panels. (e,f) A cluster of vimentin-positive cells: panel e shows a male cell after FISH in a cluster of maternal cells (arrow), and panel f shows a vimentin-positive male cell after immunolabelling (arrow). Original magnification: 1,000× for both panels.