There are two main types of breast cancer -- non-invasive and invasive.  Invasive breast cancers involve the spread of the cancer to healthy breast tissue; non-invasive breast cancers are, logically, cancers that confine themselves primarily to the ducts or lobules of the breast.

The difference between invasive and non-invasive breast cancer is a multitude of treatment options and the reaction to those treatment options.  Whether a breast cancer is one or the other determines the path that a sufferer must take for treatment.  While invasive breast cancers are significantly more serious than non-invasive cancers, it should be said that non-invasive cancers can grow into and raise your risk for an invasive cancer.

There are two main types of non-invasive breast cancers:

Ductal Carcinoma In Situ (DCIS)

Ductal carcinoma in situ makes up the majority of the cases of non-invasive breast cancer.  Contrary to the penetrating nature of invasive breast cancer, ductal carcinoma in situ stays where it began (hence in situ), inside the milk ducts of the breast. 

As such, the cancer is not life-threatening, providing early detection.  When an woman is diagnosed, treated, and cured of ductal carcinoma in situ, she has increased risk of developing another breast cancer in the future.  Similarly, those who have recovered from the cancer without using radiation therapy have their risk for recurrence raised by up to 30%.

Symptoms

Ductal carcinoma in situ usually does not display any symptoms.  A small number of cases may show symptoms of a lump in the breast or a discharge from the nipple.

Diagnosis

While most diagnoses come from mammography, a number of procedures are used to diagnose ductal carcinoma in situ.

- Physical examination: during a physical examination, a doctor or nurse may feel a small lump in the breast and/or examine the lymph nodes to search for abnormalities.  It is recommended to continually be checked by the doctor.  However, few cases of the cancer are diagnosed in this manner, as there may be no lump.

- Mammography: mammography uses an x-ray used to investigate the breast and are the most common test used to find ductal carcinoma in situ.

- Biopsy: if there is any suspicion of cancer, a biopsy may be needed.  A biopsy is performed by removing the suspected tissue and examining it under a microscope.

Lobular carcinoma in situ (LCIS)

Lobular carcinoma in situ is a non-invasive breast cancer that develops and remains in the milk-producing lobules of the breast (hence lobular).  Lobular carcinoma in situ also tends to affect more than one lobule in each case. 

The cancer is not considered a true breast cancer, but instead predicts a higher risk for developing breast cancer in the future.  As such, it is mislabeled as carcinoma and is occasionally named lobular neoplasia instead.  It is commonly found in women between the ages of 40 and 50.  Lobular carcinoma in situ displays no symptoms and is hard to detect on a mammogram.

Symptoms

As there are no displayed symptoms of lobular carcinoma in situ, most cases of it go unnoticed, even with breast examinations and mammograms. 

Diagnosis

Physical examinations and mammograms often do not diagnose lobular carcinoma in situ.  A biopsy, however, can diagnose LCIS.  In fact, the pathologist may confuse the cells of lobular carcinoma in situ with those of ductal carcinoma in situ.