Adenosis of the human breast, light micrograph. Adenosis is a benign change consisting of an enlargement of the lobules with an increased number of ductules or acini within them. Here lobules are occupied by the tubular duct lobular unit (TDLU), with a hyperplasia of terminal ducts, which is characteristic of adenosis. The intralobular stroma is rich in collagen fibres (fibrosis).