What is invasive lobular cancer (ILC)?

​Invasive lobular breast cancer (also called Infiltrating lobular breast  carcinoma) is a subtype of breast cancer which arises from the milk-producing lobules which connect to the ducts that carry milk to the nipple.  It is the second most common type of invasive breast cancer after infiltrating ductal cancer, and comprises 5-10% of all invasive lesions.

​Some Singapore breast cancer data  suggests  that it is more closely related to postmenopausal hormone replacement therapy than that of invasive ductal carcinoma.

​The word “invasive” differentiates this from “in-situ” carcinoma (such as ductal carcinoma in-situ, or lobular carcinoma in-situ) which do not have an invasive element when the cancer cells are seen under the microscope by a pathologist.

What are the distinctive signs and symptoms?

​Invasive lobular breast carcinomas often arise in women who are older and they are usually larger and more well-differentiated. ILCs often may not present with a defined mass lesion, and the excised breast tumour under the microscope may be significantly greater in size than that measured grossly.  It may be associated with in-situ lesions such as lobular carcinoma in-situ (LCIS) in two-thirds of cases and ductal carcinoma in-situ (DCIS).

​ILCs have a higher frequency of bilaterality (meaning involving both breasts) and multicentricity (meaning involving more than one area within different quadrants of the breast) compared to invasive ductal cancers. In general, they are often hormone receptor positive (oestrogen and/ or progesterone receptor positive).

​Invasive lobular breast cancers  tend to spread to distant sites later and to unusual locations such as the peritoneum (membrane that forms the lining of the abdominal cavity), gastrointestinal tract and meninges (membraneous covering of the brain and spinal cord).  At OncoCare Cancer Centre, we have seen such unusual presentation of breast cancer; it may also happen many years after the initial diagnosis of breast cancer. A confirmation of the recurrence may require a biopsy to be done to compare it with the original breast tumour.

​ILCs are known to occur in about 20-50% of women with a family history of hereditary diffuse gastric cancer who have a germline mutation in the CDH1 gene.

More interesting reads: Fun fact on triple negative breast cancer

How to diagnose invasive lobular breast cancer?

​Physical examination

Early lobular breast cancers may not have any symptoms and may only present with a mammogram or ultrasound breast abnormality, hence the importance of  going for regular breast cancer screening.

​ILCs  may  not present with  a distinct lump but instead demonstrate thickening or hardening of the tissue. Other possible symptoms include an area of breast swelling or fullness, skin changes on the breast, nipple inversion which was not present before, nipple discharge or a lymph node mass in the underarm area or above the collar bone.

Mammography

Invasive lobular breast cancers  tend to be a bit more difficult to visualize on mammograms  because the cells tend to grow in a single file pattern rather than a mass. It can also appear on the mammogram to be smaller than it actually is upon surgery.

​Ultrasound

Can be used as an adjunct to mammogram in order to visualize the specific area of abnormality.

Breast MRI

Can be useful to detect multifocality (presence of two or more foci of cancer within the same quadrant of the breast) and multicentricity as well as estimating tumour size.

​Breast Biopsy

May or may not be done via radiological guidance to obtain tissue for histology. There are various histological types of invasive lobular carcinoma although these usually do not affect treatment decisions (see Table below).