atypical lobular hyperplasia
Meaning of atypical lobular hyperplasia: A marker of raised risk in both breasts rather than a lesion that becomes cancer where it sits.
Definition of atypical lobular hyperplasia
Atypical lobular hyperplasia is a benign breast finding in which the small milk-producing sacs called lobules contain more cells than normal, and those cells look abnormal under the microscope but fill less than half of the lobule. It is not cancer and does not usually form a lump. It is found on a biopsy taken for some other reason.
How is it told apart from the neighboring diagnoses?
| Finding | What the microscope shows |
|---|---|
| Usual lobular hyperplasia | Extra cells of normal appearance |
| Atypical lobular hyperplasia | Abnormal cells filling under half the lobule |
| Lobular carcinoma in situ | The same cells filling and swelling more than half |
| Invasive lobular carcinoma | The same cells breaking out through the lobule wall |
The four sit on one continuum and the boundaries between them are matters of degree, judged by how much of the lobule is filled and stretched. Agreement between pathologists is imperfect for that reason, and the first two steps are often grouped together as lobular neoplasia. The cells in all of them share a loss of the adhesion protein E-cadherin, which is why they look loose and uncohesive rather than forming tight structures.
Why does it raise risk in both breasts?
A lesion that develops into cancer does so where it sits. This one behaves differently: the increase in breast cancer risk applies to both breasts at broadly similar rates, which points to a generalized change in the breast tissue rather than a single lesion on its way to turning malignant. The risk runs several times that of a comparable person without the finding, and it persists for decades. Both patterns can hold at once, and the same cells are sometimes found beside a cancer in the same place.
What happens after it is found?
Because the change is scattered and invisible on imaging, a needle biopsy showing it may have missed something worse a few millimeters away. Practice therefore turns on whether the imaging finding and the microscopic finding explain each other, and surgical removal of the area is sometimes undertaken to be certain. Longer term, the finding places a person in a higher risk group, which affects how often imaging is offered and whether risk-reducing medication is discussed.
How does it differ from the ductal form?
The breast holds two structures: ducts that carry milk and lobules that make it. Atypical hyperplasia in the ducts is called atypical ductal hyperplasia, and the lobular form described here is its counterpart. Both raise risk to a broadly similar degree, but the ductal form is more often flagged by calcium specks on a mammogram while the lobular form stays silent. The loss of E-cadherin is confined to the lobular cells, and that difference separates the two in difficult cases.
Also known as
Used in a sentence
Atypical lobular hyperplasia was reported incidentally on the core biopsy.
Good to know
The finding raises the risk of cancer in both breasts rather than only where it was seen, which is why it is regarded as a marker of risk as well as a possible precursor.
Word origin
Where “atypical lobular hyperplasia” comes from
Hyperplasia joins the Greek hyper, meaning over, with plasis, meaning formation; lobular comes from the Latin lobulus, a small lobe.