Ductal carcinoma in situ (DCIS) is nowadays a quite frequent diagnosis of malignancy in breast screening. But is it really cancer?
The phrase "in situ" is Latin for "in position". Translating it freely, we could name it "local ductal carcinoma". DCIS consists of cancer cells that grow inside a lactiferous duct and, unlike invasive cancer, do not infiltrate its basement membrane, do not grow beyond it and cannot metastasize. This is because these cells do not possess the biological abilities necessary in order to move and survive away from their original position. So, a ductal carcinoma in situ is basically a precancerous lesion. Not being able to metastasize, DCIS is not life-threatening.
A. Normal cells of the lactiferous duct B. Basement membrane of the lactiferous duct C. Lumen of the lactiferous duct D. Cancer cells
The problem about DCIS is that, if it is not treated, it will turn into an invasive breast cancer at an approximate 50% rate. After that may metastasize and prove life-threatening. Unfortunately, until today there has not been a safe way to identify the cases which will not turn into invasive cancer, if not treated. So, almost all cases of ductal carcinoma in situ are treated as potentially malignant.
Due to the wide use of screening, the DCIS diagnosis frequency has dramatically increased within the last decades. So, 30-40% of cancers discovered through screening with mammography are DCIS. Also, 90% of DCIS are discovered through mammography and only 10% present with clinical symptoms. The symptoms that can point to DCIS are:
Palpable mass or induration
Nipple discharge (leakage of fluid), most often bloody or serum-like
Skin lesion of the nipple (Paget's disease)
The most common mammography-based finding are microcalcifications. Microcalcifications are depositions of calcium salts that appear in the mammography as tiny white dots of various shapes. Mammography, as a test, is highly sensitive in detecting DCIS. On the other hand, breast ultrasonography has limited ability to image DCIS. This ability seems to be enhanced by the use of high-resolution ultrasounds and by the examiner's experience. The breast magnetic resonance imaging (MRI) does not have the high sensitivity it boasts with invasive cancer diagnosis; however, in cases of DCIS it may have higher sensitivity in detecting the existence of multiple foci in the same breast (multicentric disease).
The final diagnosis of a ductal carcinoma in situ is performed by means of a biopsy. The biopsy can be:
Percutaneous core needle biopsy, ultrasonography or mammography-guided.
Percutaneous vacuum-assisted core needle biopsy, ultrasonography or mammography-guided.
Open surgical biopsy. In this case, the non-palpable lesion is usually localized first using a special wire guide (hook wire).
Where there are microcalcifications, no frozen section (intraoperative biopsy) should be performed because it is possible to lose valuable information. (See the relevant article)
The treatment for DCIS aims at complete removal of the lesion and minimization of the possibility of recurrence. In cases of relapse (recurrence) of the lesion in the same breast, 50% will be invasive cancer. It is therefore understood that the first treatment of the disease is critical.
Nowadays, the method of choice for DCIS treatment is local removal of the lesion followed by breast irradiation. Surgical removal of the lesion without breast irradiation is considered insufficient, as it is accompanied by a high local relapse (recurrence) rate of the disease. Certain cases of a special type of DCIS, small lesion, at a later age constitute the exception: there local excision alone is sufficient. In some cases mastectomy might be necessary. Usually mastectomy does not need to be followed by radiation therapy. The signs pointing to a mastectomy are the following:
Very extended lesion in a small breast, where complete removal of the lesion leaves a poor aesthetic result
Multicentric lesion, i.e. existence of multiple DCIS foci at various points of the same breast
Local relapse after local excision and radiation therapy
In patients where the lesion is hormone receptor positive, especially after a local excision with or without radiation therapy, hormone therapy with tamoxifen is administered for 5 years. Administration of tamoxifen to patients with negative hormone receptors is not certainly beneficial. Administration of tamoxifen in cases of a mastectomy depends on the individual; when tamoxifen is actually administered, it principally aims at reducing the risk of a recurrence of the malignancy in the healthy breast (risk reduction therapy).
Even today, many aspects of DCIS treatment are in need of further studying and clarification. The efforts mainly focus on developing methods for identifying patients with ductal carcinoma in situ which will never turn into an infiltrating cancer. This way, overtreatment for at least half of the patients with DCIS will be prevented.