CancerQuest | Breast Cancer: Types

There are several different kinds of breast cancer. However, the majority of breast cancer cases are classified as either in situ or invasive. Both cancer types are described below.

Carcinoma In Situ

Lobular Carcinoma In Situ (LCIS)
Lobular carcinoma in situ describes breast cancer that is confined to the milk-producing glands (lobules) of the breast. Tumors classified as LCIS are made up of small uniform cells that are similar to cells found in breast lobules. LCIS will not progress to invasive breast cancer; therefore it is considered a risk factor for the development of invasive cancer rather than a true precursor. It is also referred to as lobular neoplasia (LN), a more inclusive description that also includes atypical lobular hyperplasia (ALH), another abnormal breast finding ⁽¹⁾.

Lobular carcinoma in situ is most commonly found in pre-menopausal women between the ages 40 and 50 ⁽¹⁾. It is not usually found on a mammogram and generally does not produce a lump ⁽¹⁾. These tumors are usually HER2 negative (-) and ER/PR positive (+) and therefore may be treated with hormone therapy (tamoxifen). Overall LCIS is highly treatable and in many cases continued observation is enough.

Ductal Carcinoma In Situ (DCIS)
Ductal carcinoma in situ describes breast cancer that is confined to the milk ducts of the breast. Tumors classified as DCIS are made up of irregular cells that resemble cells found in the ductal system of the breast. Unlike LCIS, DCIS can be detected on a mammogram and usually does produce a lump. DCIS accounts for 20% of all breast cancers detected with mammography and about 85% of in situ cancers diagnosed each year in the United States. Most cases of DCIS (~98%) will not become metastatic, but around 50% progress to invasive breast cancer (IBC). The progression of DCIS to IBC is not completely understood and because of this treatment recommendations vary. The most common treatment plan for DCIS is breast-conserving surgery with or without radiation.

Recurrence of DCIS is a possibility; therefore prognostic factors are calculated based on nuclear grade (most important factor), cell necrosis, and cell and tumor architecture. 50-75% of DCIS lesions are ER/PR positive and 30-50% of the time (more often in high-grade lesions) HER2 is over-expressed. DCIS that over express HER-2 are associated with a negative prognosis.⁽²⁾However, these biological markers cannot fully predict recurrence risk, but may be helpful in follow up observation and treatment planning.

Invasive Breast Carcinoma (IBC)

Images of invasive breast cancer:
breast cancer tissue

Left: Pathology slide image of cancerous breast tissue, Right: Tumor (white area) in fatty breast tissue.
Images courtesy: C. Whitaker Sewell, MD - Professor of Pathology, Emory University School of Medicine

Invasive Lobular Carcinoma (ILC)
Invasive lobular carcinoma develops in the milk-producing glands (lobules)of the breast. ILC has the ability to spread to other parts of the body, (most commonly bone, brain, liver, and lungs) either through the bloodstream or the lymphatic system. ILC usually presents as an abnormal feeling breast (most often a thickening) and not as a hard mass that can be felt. ILC is less likely to show up on a mammogram.

Women over the age of 40 have an increased risk of developing invasive lobular carcinoma, with most cases occurring in women between the ages 45-56.

Invasive Ductal Carcinoma (IDC)
Invasive ductal carcinoma is the most common type of invasive breast cancer, responsible for almost 85% of cases. IDC starts in the milk ducts and invades the surrounding tissue. IDC has the ability to move to other parts of the body (most commonly bone, brain, liver, and lungs) either through the bloodstream or the lymphatic system. IDC develops as a hard lump with irregular borders that usually shows up as a spiked mass on a mammogram.

Women over the age of 40 have an increased risk of developing invasive ductal carcinoma, with around 50% of cases occurring in women over the age of 65.