乳腺是汗腺的变异 ,来源于胚胎腹面外胚层的原始表皮。在胚胎从第 6周至胚龄第 9月的发育过程中 ,其胸区乳腺始基的原始表皮增生成芽 ,向表皮下间叶内延伸 ,逐步演变为分叶的分支管道系统。虽然 ,乳腺的来源与发育似乎是一个不大复杂的系统 ,但乳腺癌的类型却相当复杂。当今认 Breast is a variation of sweat gland, derived from the primitive epidermis of embryonic ventral ectoderm. During embryo development from the 6th week to the 9th day of embryo age, the primordial epidermal hyperplasia of the mammary gland began to bud into the subepidermal lobule and gradually evolved into a branch-branched ductal system. Although the source and development of the mammary gland seem to be a modest system, the type of breast cancer is quite complex. Now recognized