lobular carcinoma
Meaning of lobular carcinoma: A breast cancer that spreads through tissue in single file rather than forming a lump, which is why imaging so often underestimates it.
Definition of lobular carcinoma
Lobular carcinoma is a breast cancer arising in the lobules, the small glands that produce milk. Its cells lack a protein that normally binds neighboring cells together, so instead of forming a discrete lump they infiltrate in thin single-file strands through the surrounding tissue. It is the second commonest type of breast cancer after the ductal form.
Why does it behave so differently?
Almost everything distinctive about it follows from one missing protein. E-cadherin is the molecule that holds neighboring epithelial cells to each other, and in this tumor it is lost. Without it the cells do not cohere into a mass. They thread between existing structures in single files, leaving the architecture of the breast largely intact. The result is a vague thickening or a change in texture rather than a firm discrete lump, and often nothing that can be felt at all until the area involved is large.
Why is it harder to detect?
| Method | Why it can miss the tumor |
|---|---|
| Examination | No distinct lump forms |
| Mammogram | Density resembles normal tissue; calcifications uncommon |
| Ultrasound | Margins are ill defined |
| MRI | Most sensitive, and often shows the extent to be greater than expected |
The practical consequence is that the disease is more often found at a larger size than the ductal type, and that the extent seen at surgery exceeds what imaging suggested, which is a common reason a first operation fails to clear the margins.
How does the in situ form relate to it?
Lobular carcinoma in situ is a different thing from its name. It is not a cancer confined by a boundary in the way ductal carcinoma in situ is. It is a marker of raised risk, indicating an increased chance of invasive cancer developing later in either breast, of either type. That is a wholly different implication, and the misleading name has led to a preference for calling it lobular neoplasia.
What is characteristic of its behavior?
It is more often hormone receptor positive and less often HER2 driven than the ductal form, so hormone-directed treatment carries more weight. It appears in both breasts more frequently. When it spreads it favors unusual destinations, reaching the lining of the abdomen, the ovaries, the stomach and the marrow more often than the lung, and the diffuse growth pattern makes these deposits difficult to see on scans.
Also known as
Used in a sentence
Invasive lobular carcinoma was reported with an extent exceeding the mammographic estimate.
Good to know
Loss of the cell adhesion protein E-cadherin explains the single-file growth, the absence of a discrete lump and the frequent underestimation of tumor extent on imaging.
Word origin
Where “lobular carcinoma” comes from
Lobular comes from the Latin lobulus, a small lobe; carcinoma from the Greek karkinos, meaning crab, with the tumor ending -oma.