Human milk fat globulin 1 (HMFG) and gross cystic disease fluid protein 15 (GCDFP-15), which is regarded as a marker of apocrine epithelium [7,8], were weakly positive in some cells of the cyst wall, showing decapitation secretion, while being strongly positive in the cells of all of the above described glandular groups. Here, PIP is linked to cyst.