Generality
The nipple is a conical or cylindrical protrusion located at the apex of the breast . This structure represents the point where the glandular (or galactophore) ducts flow together, to open up to the external surface of the body.
Compared to the skin surface, the nipple is more or less detected. Occasionally, this can be retracted under the skin surface, but, if stimulated, it ejects upwards and outwards. When it remains permanently inverted, however, we talk about reversing the nipple; this condition is abnormal and must be controlled from a medical point of view.
The nipple may be the site of various pathological processes, including malformations, infections, traumas and neoplasms.
Anatomy
The breast is an organ made up of glandular tissue (organized in lobules), a series of ducts (which carry milk up to the nipple) and a part of adipose tissue.
At the apex of the breast, the nipple is found, that is a relief of conical or cylindrical appearance, more or less protruding and pigmented (generally of a dark pink or brown color).
Usually, this structure is located at the level of the fourth intercostal space, on the hemiclavear line (ie slightly below the middle of the chest), but the position is inconstant, since the breasts are hanging.
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 ( cribrosa area ) from dimples and papillae, in which 15-20 galactophore ducts open; in fact, on its surface, one can observe the small outlet openings.
The nipple also contains smooth muscle tissue, arranged circularly and radially, and responsible for its erection.
The nipple is surrounded by the mammary areola, that is by an area of glabrous skin of circular shape (with a diameter of a couple of centimeters). The latter contains the Montgomery glands (important for making the nipple soft and elastic during lactation), and, sometimes, also for the accessory breast tissue, which becomes evident with the milk secretion.
Development and functions
- During the first years of life, the nipple is small. Upon reaching puberty, this structure increases in volume particularly in women, while it remains "rudimentary" in the male. During pregnancy and lactation, the nipple reaches its maximum development, becoming more prominent and pigmented.
- Under the influence of direct or reflex stimuli, the nipple goes into an erection 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 is to eject the breast milk in the period following the birth event. This phenomenon allows the start of breastfeeding.
The milk is produced in the udders by a set of acinar glands (called alveoli) and is carried to the nipples through the galactophore ducts. In fact, after giving birth, 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 get milk, the baby simply has to suck the nipples (known as sucking ), causing a flow of milk through the ducts.
Suction stimulates the contraction of the myoepithelial cells that surround the alveoli and pushes the milk to flow through the galactophore ducts ( ejection ).
Alterations and symptoms
Nipple inversion
Normally, the nipples are protruding. In some cases, however, they appear introflexed, therefore re-entering the breast, even if stimulated manually or with cold.
The nipple inversion is often a benign condition, but it can also indicate the presence of a more severe problem. This anomaly can affect only one breast or both.
The nipple inversion may be present from birth (due to the shortness of congenital galactophore ducts ) or acquired. In the latter case, the retraction is sustained, in most cases, by periductal fibrosis resulting from inflammatory processes or surgery. If the nipple does not protrude, it can interfere with the normal possibility of breastfeeding.
Sometimes, nipple inversion may represent the first sign of a breast neoplasm, especially when it is asymmetrical or associated with blood secretion or the presence of a nodule.
| Nipple inversion | |
| Benigna | Malignant |
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Nipple secretion
In some cases, in response to the manipulation of the udder or spontaneously, from the ducts can be squeezed a small amount of transparent liquid or of yellow, white or green color. This manifestation can occur in male individuals or in women, outside the period of pregnancy and breastfeeding.
Serum secretion can be an abnormal or harmless symptom; a blood loss from the nipple (at a microscopic and macroscopic level) is never, however, to be considered normal.
For this reason, the causes of these secretions must be investigated. The most serious condition related to this sign is, instead, breast cancer (usually intraductal or invasive ductal carcinoma). In most cases, however, the cause is benign and attributable to pathologies of benign mammary ducts (eg ductal ectasia and intraductal papilloma) or sinus infections (mastitis).
Galactorrhea
Galactorrhea is the secretion of a milky, non-puerperal serum from different ducts of both breasts.
Often, this phenomenon is due to a prolactin-secreting pituitary adenoma ( prolactinoma ), a hormone that at high levels stimulates the glandular tissue of the breast.
Galactorrhea may also depend on hypothalamic tumors and other endocrine disorders, such as acromegaly, thyrotoxicosis, primary hypothyroidism and Cushing's disease.
Supernumerary nipples (polythelia)
In addition to the typical site, the nipples can develop in supernumerary, usually along two breast lines, which run from the armpits to the groin. Polythelia is a generally sporadic condition, but it can also recognize a genetic predisposition.
The supernumerary nipples can appear as simple pigmented patches, similar to the moles.
malformations
The nipple-related malformations are attributable to changes in its shape. These conditions can be detrimental to breastfeeding: the structure can be too bulky, short or even absent, making sucking more difficult.
Sometimes, then, instead of protruding, the nipple appears umbilicated, that is flat or re-entered at the center of the mammary areola, due to its embryonic development.
Peeling of the nipple
Nipple peeling is a manifestation associated mostly with dried nipple secretions. On some occasions, however, this sign may depend on an eczematous type of injury. Other times, peeling of the nipple indicates the presence of Paget's disease or erosive adenoma.
Main pathologies of the nipple
fissures
The fissures are small particularly painful fissures, which are found especially during the period of breastfeeding. These lesions deepen beyond the dermis and can be circular (ie around the nipple implant on the areola) or running from the apex to the base of the nipple. This condition may favor the colonization of the galactophores by infectious agents.
Often, the nipple fissures regress spontaneously with the withdrawal of breastfeeding.
Paget's disease of the nipple
Nipple Paget's disease is a malignant tumor that derives from the proliferation in the neoplastic sense of the cells of the galactophore ducts. The disease usually affects only one breast and is often associated with ductal breast cancer in situ or invasive type. The risk factors that predispose the onset are the same that make it 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 (the appearance is similar to that of a psoriatic plaque or an eczema). In about half of all cases, an underlying breast lump can be seen on palpation. Other frequent symptoms of Paget's disease are straw-colored secretions (serous or purulent), itching and a burning sensation around the nipple and mammary areola. In addition, edema, nipple introflection and ulcerative-erosive lesions with crusting may occur.
Nipple Paget's disease can be diagnosed with a biopsy, but given the possible association with breast cancer, other medical investigations such as mammography and MRI can be performed.
The treatment involves the surgical removal of the diagnosed tumors (conservative or radical). Depending on the case, an adjuvant treatment with chemotherapy drugs, radiotherapy or hormone therapy may also be recommended, in order to prevent recurrent breast cancer and destroy any remaining cancer cells.
Eczema of the nipple and areola
Eczema can involve areolas and / or nipples to varying degrees and can be part of a generalized skin disorder. However, it may 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 involved with molluscum contagiosum (swelling with associated ulcer), herpetic lesions and condyloma.
Sebaceous cysts
The sebaceous cysts of the nipple are rare. This condition manifests itself as a painless swelling closely related to the nipple, and communicating or not with a duct galactophore. Sebaceous cysts can become infected.
Traumatic injuries
One or both nipples may be affected by protracted friction caused by a shirt or other clothing, especially when performing a sport. The people most exposed to this condition are those who practice running (hence the name "nipple of the runner") or breastfeeding. In most cases, this trauma is associated with the presence of sweat and heat and can cause irritation, redness of the skin, soreness, dryness or bleeding.
The friction associated with the cold can result, instead, in painful lesions, often with aspects similar to those of eczema and, sometimes, with micro-hemorrhages simulating the nipple's blood secretions. This last condition is found above all among cyclists.
Erosive adenoma of the nipple
The erosive adenoma is a rare condition in which the nipple appears increased in volume, sometimes ulcerated and bleeding. In addition, burning or itching pain is reported. The diagnosis of erosive adenoma is confirmed with a biopsy. The treatment does not require the removal of the whole nipple, but only of the affected part.
