2 The Terminal Duct Lobular Unit (TDLU)

The micro-anatomical structure, the ‘terminal duct lobular unit’ or TDLU has become central to understanding the origins of breast disease, including breast cancer. The TDLU (also named ‘Type 1 lobule’ ) has the highest rate of epithelial cell proliferation that are more numerous in the breasts of nulliparous women.

What is a nulliparous woman?

A nulliparous refers to a woman who has never carried a pregnancy beyond 20 weeks.

The epithelial components of the breast, the lobules and ducts, produce and deliver milk during lactation. In the female who is post menarche and pre-menopause, these glandular elements undergo cyclical changes in response to the female hormonal cycle.

Breast lobular and ductal epithelial cells possess estrogen receptors (ER) and progesterone receptors (PR).

The branching ducts connect the lobules of the breast to the nipple.

Oh it’s very complicated, what is post menarche even? I have brain ache now.

Quite simply put, women who menstruate have monthly breast changes.

The Terminal Duct Lobular Unit (TDLU)

Diagram of the non-lactating breast showing the arrangement of the ducts and lobules.
B. Low power photomicrograph of the histology of the normal terminal duct and lobule (TDLU) with the Alveolus, Epithelium and basement membrane (*)

For a patient who has had a breast abnormality sampled or removed, the Pathologist will produce a written report with a diagnosis. This diagnosis will allow the physician to manage patient care.

The following are the benign diagnoses that may be found at the end of a Pathology report.