What Is Nipples: Structure, Functions and Diseases, Development And Functions,Changes And Symptoms, Erosive Adenoma Of The Nipple


The nipple is a conical or cylindrical protrusion located at the apex of the breast . This structure represents the point where the glandular ducts (or galactophores) converge, to open up to the external surface of the body.

The nipple is hyperpigmented and has a soft and supple texture. At its top, this is wrinkled in appearance, due to the presence of the small outlet orifices of the lactiferous ducts . The latter transport the milk produced by the mammary gland to the outside .
Compared to the skin plane, the nipple is more or less raised. Occasionally, this may be retracted under the skin surface, but, when stimulated, it will flex upward and outward. When it remains permanently inverted, however, we speak of nipple inversion ; this condition is abnormal and should be medically controlled.

The nipple can be the site of various pathological processes, including malformations, infections, traumas and neoplasms.


The breast is an organ made up of glandular tissue (organized in lobules), a series of ducts (which carry the milk up to the nipple) and a part of adipose tissue .
At the apex of the breast, there is the nipple , i.e. a conical or cylindrical relief, more or less protruding and pigmented (generally dark pink or brown).

Usually, this structure is located at the level of the fourth intercostal space, on the midclavicular line (i.e., slightly below the middle of the chest), but the position is inconstant, as the breasts are pendant.
The size of the nipple is usually proportional to that of the breast: the relief has an average height of 10-12 mm and a diameter of 9-10 mm.
The skin that covers it is corrugated ( cribrous area ) by dimples and papillae, in which 15-20 lactiferous ducts open; in fact, on its surface, small outlet orifices can be observed.

The nipple also contains smooth muscle tissue , arranged circularly and radially, and responsible for its erection .
The nipple is surrounded by the mammary areola , i.e. by a circular area of ​​glabrous skin (with a diameter of a couple of centimetres). The latter contains the Montgomery glands (important for making the nipple soft and supple during breastfeeding ) , and sometimes also accessory mammary tissue, which is evident with the milky secretion .

Development And Functions

  • During the first years of life, the nipple is small in size. Upon reaching puberty , this structure increases in volume particularly in females, while it remains “rudimentary” in males. During pregnancy and breastfeeding, the nipple reaches its maximum development, becoming more prominent and pigmented.
  • Under the influence of direct or reflex stimuli, the nipple becomes erect, lengthening and increasing in consistency; this phenomenon, called telotism , is due to the presence of smooth muscle cells similar to those of the areolar muscle.
  • In both men and women, the nipples also represent an erogenous zone . Their prolonged and intense stimulation during sexual activity can therefore lead to excitement.
  • The main physiological purpose of the nipples consists in the ejection of mother’s milk in the period following the birth event . This phenomenon allows the initiation of lactation.

Milk is produced in the breasts by a set of acinar glands (called alveoli) and is carried to the nipples through the lactiferous ducts. After birth, in fact, the decrease in estrogen and progesterone allows the stimulating effect of prolactin on the secretion of milk by the cells of the alveoli and allows lactation to take place.
To obtain milk, the newborn simply has to suck on the nipples (an act known as sucking ), resulting in a flow of milk through the ducts.

Sucking stimulates the contraction of the myoepithelial cells surrounding the alveoli and pushes the milk to flow through the lactiferous ducts ( ejection ).

Changes And Symptoms

Nipple inversion

Normally, the nipples are protruding. In some cases, however, they appear inward, therefore retracting into the breast, even if stimulated manually or with cold .
Nipple inversion is often a benign condition, but it can also indicate a more serious problem. This anomaly can affect only one breast or both.
Nipple inversion can be present from birth (due to congenital shortness of the lactiferous ducts ) or acquired. In the latter case, the retraction is most often supported by a periductal fibrosis resulting from inflammatory processesor surgery. If the nipple is not protruding, it can interfere with the normal ability to breastfeed.
Sometimes, nipple inversion can be the first sign of breast cancer , especially when it is asymmetrical or associated with bloody discharge or the presence of a lump .

Nipple inversion
Benign Malicious
  • Symmetrical
  • Similar to a crack
  • Asymmetrical
  • Distorting the nipple, which appears deviated to one side

Nipple Discharge

In some cases, a small amount of clear or yellow, white, or green liquid may be squeezed out of the ducts in response to manipulation of the breast or spontaneously . This manifestation can occur in males or in women, outside the period of pregnancy and breastfeeding .  Serum discharge
may be an abnormal or harmless symptom; however, a blood loss from the nipple (at a microscopic and macroscopic level) is never to be considered normal. For this reason, the causes of these secretions should be investigated. The most serious condition referred to by this sign is, however, breast cancer (usually
intraductal or invasive ductal carcinoma ). In most cases, however, the cause is benign and attributable to benign mammary duct disease (eg, ductal ectasia and intraductal papilloma) or breast infection ( mastitis ).


Galactorrhea is the secretion of a milky, non-puerperal serum from several ducts of both breasts.

Often, this phenomenon is due to a prolactin-secreting pituitary adenoma ( prolactinoma ), a hormone that stimulates the glandular tissue of the breast at high levels.
Galactorrhea may also result from hypothalamic tumors and other endocrine disorders, such as acromegaly , thyrotoxicosis , primary hypothyroidism, and Cushing ‘s disease .

Supernumerary Nipples (Polythelia)

In addition to the typical location, the nipples can develop in excess, usually along two mammary lines, which run from the armpits to the groin. Polythelia is generally a sporadic condition, but it can also recognize a genetic predisposition.
Supernumerary nipples can present as simple pigmented patches, similar to moles.


The malformations affecting the nipple are referable to variations in its shape. These conditions can hinder breastfeeding: the structure can be too bulky, short or even absent, making sucking more difficult.
Sometimes, then, instead of protruding, the nipple appears umbilicated, i.e. flat or returned to the center of the mammary areola, due to the arrest of its embryonic development .

Nipple Peeling

Nipple flaking is a manifestation associated mostly with dried discharge on the nipple. On some occasions, however, this sign may depend on an eczematous lesion . Other times, nipple peeling indicates the presence of Paget’s disease or erosive adenoma .

Main Pathologies Of The Nipple


Fissures are small , particularly painful fissures, which are found above all during the breastfeeding period. These lesions deepen beyond the dermis and can have a circular pattern (ie around the nipple implant on the areola) or run from the apex to the base of the nipple. This condition can favor the colonization of the lactiferous ducts by infectious agents. Nipple fissures
often resolve spontaneously when breastfeeding is stopped.

Paget’S Disease Of The Nipple

Paget’s disease of the nipple is a malignant tumor resulting from the neoplastic proliferation of the cells of the lactiferous ducts. The disease usually affects only one breast and is often associated with ductal in situ or invasive breast cancer . The risk factors that predispose the onset are the same ones that make one susceptible to the development of other types of breast cancer.
Paget’s disease produces visible changes in the skin of the nipple-areola complex: the skin appears red, dry, irritated, or scaly (appears similar to a psoriatic plaque or eczema). In about half of all cases, an underlying breast lump can be found on palpation. Other frequent symptoms of Paget’s disease are straw-colored discharge (serous or purulent ), itching and burning sensation around the nipple and breast areola. In addition, edema , introflection of the nipple and ulcerative-erosive lesions with crusting may occur .
Paget’s disease of the nipple can be diagnosed with a biopsy , but other medical tests, such as mammography andMRI .
Treatment involves surgical removal of the diagnosed tumors (conservative or radical) . Depending on the case, adjuvant intervention with chemotherapy drugs , radiation therapy or hormone therapy may also be recommended, in order to prevent recurrence of breast cancer and destroy any remaining cancer cells.

Eczema Of The Nipple And Areola

Eczema can involve the areola and/or nipple to varying degrees and can be part of a generalized skin disorder. However, it can also be due to Paget’s disease of the nipple or invasion of the epidermis by an intraductal breast tumor.

Viral Infections

The nipple area may sometimes be affected by molluscum contagiosum (swelling with associated ulcer), herpetic lesions and warts .

Sebaceous cysts

Sebaceous cysts of the nipple are rarely found. This condition manifests itself as a painless swelling closely related to the nipple, and communicating or not with a lactiferous duct. Sebaceous cysts can become infected.

Traumatic injuries

One or both nipples can be affected by the continued friction caused by a shirt or other clothing, especially during the performance of a sporting activity. The people most exposed to this disease are those who run ( hence the name “runner’s nipple”) or breastfeed. In most cases, this trauma is associated with the presence of sweat and heat and can cause skin irritation, redness , soreness, dryness or bleeding.
The friction associated with the cold can instead result in painful lesions, often with aspects similar to those of eczema and, sometimes, with micro- haemorrhage simulating bloody discharge from the nipple. The latter condition is found above all among cyclists.

Erosive Adenoma Of The Nipple

Erosive adenoma is a rare condition in which the nipple appears enlarged, sometimes ulcerated and bleeding. Also, a burning or itchy pain is reported. The diagnosis of erosive adenoma is confirmed with a biopsy. The treatment does not require the removal of the entire nipple, but only of the affected part.

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