MT1E and neoplasm: Accordingly, 3D and confocal fluorescent microscopy of normal mammary glands from tumor-free mice confirmed that all the ducts and alveoli of the mammary gland were GFP+, as expected (Figure 1B,C), whereas nonepithelial-derived mammary gland tissues such as adipose and connective-tissues (fibroblasts) were mTd+ (Figure 1B,C).