Paget's disease of the nipple (or mammary Paget disease) is an uncommon form of breast cancer characterized by the accumulation of cancer cells in or surrounding the nipple. It occurs in less than 5% of diagnosed breast cancer patients and is most common in women after the age of 50. Despite this, occurrence in adolescents and in the elderly is not unheard of.

Paget's disease usually begins in the milk-carrying ducts of the nipple before spreading to the exterior surface of the nipple and the areola, which become flaky, reddened, and irritated. In most cases, the disease affects only one breast, not both.

Symptoms

While the symptoms initially tend to come and go, they usually worsen with time. The symptoms include:

• Itching, tingling, redness, and/or a burning sensation in the affected nipple
• Sensitivity and pain
• Flaking of scales and skin thickening of the affected nipple
• Flattening or turning inwards (inversion) of the nipple
• Discharge (yellowish or bloody) from the nipple

Paget's disease of the nipple is rare; therefore it is very commonly misdiagnosed as skin conditions including eczema. In fact, it may take several months to receive a correct diagnosis. The fact that  over 97% of those with the disease also suffer from cancer elsewhere in the breast highlights the need for symptom awareness.

Pathophysiology

The underlying reason for the condition is not yet established. It might be that tumor growth initiates in ducts before migrating to the external surface of the nipple. This could also offer a suggestion as to why such a great number with the disease present with a second cancerous region within the breast.

Alternatively, the condition may arise when the cells of the nipple(s) develop malignant potential. This model would support the low frequency of cases with only Paget's disease, or with a second form of breast cancer appearing independent of the Paget's disease.

Diagnosis

Diagnosis is usually comprised of the following steps:

• Physical examination - special attention must be paid to the area around the nipple and a lump or mass in the breast may be felt.
• A mammogram – this is required to check the nipple area and detect evidence of cancerous tissue elsewhere in the breast.
• Ultrasound and/or MRI – this is to create additional images of the breast and, like a mammogram, can locate other cancerous areas.
• Biopsy – this is for examination of the nipple and areola tissue under a microscope. Any abnormal discharge from the breast is also analyzed.

Treatment and Prognosis

Mastectomy had been considered the first line of treatment for many years because patients were more commonly found to have more than one tumor within the same breast.

A sentinel lymph node biopsy is highly recommended for anyone with Paget disease of the nipple undergoing a mastectomy – this will test for the spread of cancer to the axillary lymph nodes. A positive result from this will likely indicate the need for a more extensive surgical approach targeting the axillary lymph node.

Recent studies have shown that breast-conserving surgery that includes removal of the nipple and areola, and subsequent whole-breast radiation therapy, is a viable and safe option for this cancer. This is provided that there is no palpable lump in the breast and tumor detected by mammogram.

The prognosis depends greatly on the stage of cancer and additional characteristics of the breast tumor cells – for example, the presence of hormone receptors for estrogen and progesterone would indicate a need for adjuvant therapy.

The overall prognosis can be determined by considering the following characteristics in the affected breast:

• Presence (or absence) of  a tumor
• Whether any tumor(s)  is invasive breast cancer or ductal carcinoma in situ
• If relevant, the stage of invasive breast cancer

References

• http://www.nhs.uk/conditions/pagets-disease-of-the-nipple/Pages/introduction.aspx
• http://www.breastcancer.org/symptoms/types/pagets
• http://www.macmillan.org.uk/information-and-support/breast-cancer/understanding-cancer/types-of-breast-cancer/pagets-disease.html
• http://www.cancer.gov/types/breast/paget-breast-fact-sheet
• http://www.cancerresearchuk.org/about-cancer/type/breast-cancer/about/types/pagets-disease
• http://www.dermnetnz.org/site-age-specific/paget.html
• http://www.hopkinsmedicine.org/breast_center/breast_cancers_other_conditions/pagets_disease.html