Through immunofluorescence examination of ErbB2 localization in ErbB2-positive breast cancer cells, we observed that, in SKBR3 and AU565 cells that possessed round shapes, ErbB2 was almost exclusively distributed to the cell membrane; while in HCC1954 cells that showed flattened and spread-out configurations, ErbB2 also formed many intracellular punctae besides surface localizations (Fig. 1a). Here, ERBB2 is linked to breast cancer.