Breast cancer risk is elevated for defined fraction of lesions. Except for patients with a strong family history of breast cancer, where the risk is two-fold, nonproliferative lesions have no increased risk. Proliferative lesions also have approximately a 2-fold risk. In particular, atypical hyperplasia is associated with an increased risk of developing breast cancer. Atypical lobular hyperplasia is associated with the greatest risk, approximately 5-fold and especially high relative risk of developing premenopausal breast cancer. Atypical ductal hyperplasia is associated with 2.4-fold risk. In contrast, a New England Journal of Medicine article states that for women with a strong familial history of breast cancer, the risk of future breast cancer is roughly doubled, independent of histological status. The article further states "The relative risk of breast cancer for the cohort was 1.56 (95 percent confidence interval, 1.45 to 1.68), and this increased risk persisted for at least 25 years after biopsy. The relative risk associated with atypia was 4.24 (95 percent confidence interval, 3.26 to 5.41), as compared with a relative risk of 1.88 (95 percent confidence interval, 1.66 to 2.12) for proliferative changes without atypia and of 1.27 (95 percent confidence interval, 1.15 to 1.41) for nonproliferative lesions. The strength of the family history of breast cancer, available for 4808 women, was a risk factor that was independent of histologic findings. No increased risk was found among women with no family history and nonproliferative findings. In the first 10 years after the initial biopsy, an excess of cancers occurred in the same breast, especially in women with atypia."

It is not well understood whether the lesions are precursors of breast cancer or only indication of increased risk, for most types of lesions the chance of developing breast cancer is nearly the same in the affected and unaffected breast (side) indicating only coincidence of risk factors. For atypical lobular hyperplasia there is high incidence of ipsilateral breast cancers indicating a possible direct carcinogenetic link.

Among women worldwide, breast cancer is the most common cause of cancer death. Breast self-examination (BSE) is an easy but unreliable method for finding possible breast cancer. Factors that appear to be implicated in decreasing the risk of, early diagnosis of. or recurrence of breast cancer are regular breast examinations by health care professionals, regular mammograms, self-examination of breasts, healthy diet, and exercise to decrease excess body fat.

90% of cases are smokers, however only a very small fraction of smokers appear to develop this lesion. It has been speculated that either the direct toxic effect or hormonal changes related to smoking could cause squamous metaplasia of lactiferous ducts. It is not well established whether the lesion regresses after smoking cessation.

Extrapuerperal cases are often associated with hyperprolactinemia or with thyroid problems. Also diabetes mellitus may be a contributing factor in nonpuerperal breast abscess.

Duct ectasia of the breast or mammary duct ectasia or plasma cell mastitis is a condition in which the lactiferous duct becomes blocked or clogged. This is the most common cause of greenish discharge.

Mammary duct ectasia can mimic breast cancer. It is a disorder of peri- or post-menopausal age.

"Duct ectasia syndrome" is a synonym for nonpuerperal mastitis but the term has also been occasionally used to describe special cases of fibrocystic diseases, mastalgia or as a wastebasket definition of benign breast disease.

Correlation of duct widening with the "classical" symptoms of duct ectasia syndrome is unclear. However, duct widening was recently very strongly correlated with noncyclic breast pain.

Duct diameter is naturally variable, subject to hormonal interactions. Duct ectasia syndrome in the classical meaning is associated with additional histological changes.

The term has several meanings on histological and symptomatic levels and on both levels "usage" overlaps with mastalgia, fibrocystic disease and specific sub- or superclasses of nonpuerperal mastitis. While this is not ideal for a definition it results from actual usage in international literature. Because research literature regarding duct ectasia is anything but abundant it is probably easiest to determine the exact meaning(s) intended by the respective authors on a case by case basis and this section can offer only a few hints.

Typical usage in North America is a synonym of nonpuerperal mastitis, including the special cases of granulomatous mastitis, comedo mastitis, subareolar abscess with or without squamous metaplasia of lactiferous ducts and fistulation.

Simple duct widening should be carefully distinguished from more complex histological changes.

Breast diseases can be classified either with disorders of the integument, or disorders of the reproductive system. A majority of breast diseases are noncancerous.

Smoking tobacco appears to increase the risk of breast cancer, with the greater the amount smoked and the earlier in life that smoking began, the higher the risk. In those who are long-term smokers, the risk is increased 35% to 50%. A lack of physical activity has been linked to about 10% of cases. Sitting regularly for prolonged periods is associated with higher mortality from breast cancer. The risk is not negated by regular exercise, though it is lowered.

There is an association between use of hormonal birth control and the development of premenopausal breast cancer, but whether oral contraceptives use may actually cause premenopausal breast cancer is a matter of debate. If there is indeed a link, the absolute effect is small. Additionally, it is not clear if the association exists with newer hormonal birth controls. In those with mutations in the breast cancer susceptibility genes "BRCA1" or "BRCA2", or who have a family history of breast cancer, use of modern oral contraceptives does not appear to affect the risk of breast cancer.

The association between breast feeding and breast cancer has not been clearly determined; some studies have found support for an association while others have not. In the 1980s, the abortion–breast cancer hypothesis posited that induced abortion increased the risk of developing breast cancer. This hypothesis was the subject of extensive scientific inquiry, which concluded that neither miscarriages nor abortions are associated with a heightened risk for breast cancer.

A number of dietary factors have been linked to the risk for breast cancer. Dietary factors which may increase risk include a high fat diet, high alcohol intake, and obesity-related high cholesterol levels. Dietary iodine deficiency may also play a role. Evidence for fiber is unclear. A 2015 review found that studies trying to link fiber intake with breast cancer produced mixed results. In 2016 a tentative association between low fiber intake during adolescence and breast cancer was observed.

Other risk factors include radiation and shift-work. A number of chemicals have also been linked, including polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and organic solvents Although the radiation from mammography is a low dose, it is estimated that yearly screening from 40 to 80 years of age will cause approximately 225 cases of fatal breast cancer per million women screened.

"Duct ectasia" in the literal sense (literally: duct widening) is a very common and thus rather unspecific finding, increasing with age. However, in the way in which the term is mostly used, duct ectasia is an inflammatory condition of the larger-order lactiferous ducts. It considered likely that the condition is associated with aseptic (chemical) inflammation related to the rupture of ducts or cysts. It is controversial whether duct dilation occurs first and leads to secretory stasis and subsequent periductal inflammation or whether inflammation occurs first and leads to an inflammatory weakening of the duct walls and then stasis. When the inflammation is complicated by necrosis and secondary bacterial infection, breast abscesses may form. Subareolar abscess, also called Zuska's disease (only nonpuerperal case), is a frequently aseptic inflammation and has been associated with squamous metaplasia of the lactiferous ducts.

The duct ectasia—periductal mastitis complex affects two groups of women: young women (in their late teens and early 20s) and perimenopausal women. Women in the younger group mostly have inverted nipples due to squamous metaplasia that lines the ducts more extensively compared to other women and produces keratin plugs which in turn lead to duct obstruction and then duct dilation, secretory stasis, inflammation, infection and abscess. This is not typically the case for women in the older group; in this group, there is likely a multifactorial etiology involving the balance in estrogen, progesterone and prolactin.

Treatment of mastitis and/or abscess in nonlactating women largely the same as that of lactational mastitis, generally involving antibiotics treatment, possibly surgical intervention by means of fine-needle aspiration and/or incision and drainage and/or interventions on the lactiferous ducts (for details, "see also" the articles on treatment of mastitis, of breast abscess and of subareolar abscess). Additionally, an investigation for possible malignancy is needed, normally by means of mammography, and a pathological investigation such as a biopsy may be necessary to exclude malignant mastitis. Although no "causal" relation with breast cancer has been established, there appears to be an increased statistical risk of breast cancer, warranting a long-term surveillance of patients diagnosed with non-puerperal mastitis.

Nonpuerperal breast abscesses have a higher rate of recurrence compared to puerperal breast abscesses. There is a high statistical correlation of nonpuerperal breast abscess with diabetes mellitus (DM). On this basis, it has recently been suggested that diabetes screening should be performed on patients with such abscess.

Risk factors can be divided into two categories:

- "modifiable" risk factors (things that people can change themselves, such as consumption of alcoholic beverages), and

- "fixed" risk factors (things that cannot be changed, such as age and biological sex).

The primary risk factors for breast cancer are being female and older age. Other potential risk factors include genetics, lack of childbearing or lack of breastfeeding, higher levels of certain hormones, certain dietary patterns, and obesity. Recent studies have indicated that exposure to light pollution is a risk factor for the development of breast cancer.

There are usually no adverse side effects to this condition. In almost all cases it subsides after menopause. A possible complication arises through the fact that cancerous tumors may be more difficult to detect in women with fibrocystic changes.

The most common causes of nipple inversion include:

- Born with condition

- Trauma which can be caused by conditions such as fat necrosis, scars or it may be a result of surgery

- Breast sagging, drooping or ptosis

- Breast cancer

- breast carcinoma

- Paget's disease

- Inflammatory Breast Cancer (IBC)

- Breast infections or inflammations

- mammary duct ectasia

- breast abscess

- mastitis

- Genetic variant of nipple shape such as

- Weaver syndrome

- congenital disorder of glycosylation type 1A & 1 L

- Kennerknecht-Sorgo-Oberhoffer syndrome

- Gynecomastia

- Holoprosencephaly, recurrent infections and monocytosis

- Tuberculosis

Around 10–20% of all women are born with this condition. Most common nipple variations that women are born with are caused by short ducts or a wide areola muscle sphincter.

Inverted nipples can also occur after sudden and major weight loss.

Treatment is problematic unless an underlying endocrine disorder can be successfully diagnosed and treated.

A study by Goepel and Panhke provided indications that the inflammation should be controlled by bromocriptine even in absence of hyperprolactinemia.

Antibiotic treatment is given in case of acute inflammation. However, this alone is rarely effective, and the treatment of a subareaolar abscess is primarily surgical. In case of an acute abscess, incision and drainage are performed, followed by antibiotics treatment. However, in contrast to peripheral breast abscess which often resolves after antibiotics and incision and drainage, subareaolar breast abscess has a tendency to recur, often accompanied by the formation of fistulas leading from inflammation area to the skin surface. In many cases, in particular in patients with recurrent subareolar abscess, the excision of the affected lactiferous ducts is indicated, together with the excision of any chronic abscess or fistula. This can be performed using radial or circumareolar incision.

There is no universal agreement on what should be the standard way of treating the condition. In a recent review article, antibiotics treatment, ultrasound evaluation and, if fluid is present, ultrasound-guided fine needle aspiration of the abscess with an 18 gauge needle, under saline lavage until clear, has been suggested as initial line of treatment for breast abscess in puerperal and non-puerperal cases including central (subareolar) abscess (see breast abscess for details). Elsewhere, it has been stated that treatment of subareolar abscess is unlikely to work if it does not address the ducts as such.

Duct resection has been traditionally used to treat the condition; the original Hadfield procedure has been improved many times but long term success rate remains poor even for radical surgery. Petersen even suggests that damage caused by previous surgery is a frequent cause of subareolar abscesses. Goepel and Pahnke and other authors recommend performing surgeries only with concomitant bromocriptine treatment.

In one report, about 20% of individuals with mealtime syndrome had strictures upon sialography. For unknown reasons, strictures seem to be more common in females.

A Gartner's duct cyst (sometimes incorrectly referred to as "vaginal inclusion cyst") is a benign vaginal cystic lesion that arises from the Gartner's duct, which is a vestigial remnant of the mesonephric duct (wolffian duct) in females. They are typically small asymptomatic cysts that occur along the lateral walls of the vagina, following the course of the duct. They can present in adolescence with painful menstruation (Dysmenorrhea) or difficulty inserting a tampon. They can also enlarge to substantial proportions and be mistaken for urethral diverticulum or other structures.

There is a small association between Gartner's duct cysts and metanephric urinary anomalies, such as ectopic ureter & ipsilateral renal hypoplasia. Because of this, imaging is recommended before excision.

Fibrosclerosis of the breast is most frequently used to mean sclerosing lobular adenosis of the breast. It is not well known if it is related to non-sclerosing adenosis of the breast (which is normally classified as fibrocystic breast changes) and unlike this it is believed to be correlated with an elevated risk of breast cancer.

Nipple discharge refers to any fluid that seeps out of the nipple of the breast. Discharge from the nipple does not occur in lactating women. And discharge in non-pregnant women or women who are not breasfeeding may not cause concern. Men that have discharge from their nipples are not typical. Discharge from the nipples of men or boys may indicate a problem. Discharge from the nipples can appear without squeezing or may only be noticeable if the nipples are squeezed. One nipple can have discharge while the other does not. The discharge can be clear, green, bloody, brown or straw-colored. The consistenct can be thick, thin, sticky or watery.

Some cases of nipple discharge will clear on their own without treatment. Nipple discharge is most often not cancer (benign), but rarely, it can be a sign of breast cancer. It is important to find out what is causing it and to get treatment. Here are some reasons for nipple discharge:

- Pregnancy

- Recent breastfeeding

- Rubbing on the area from a bra or t-shirt

- Trauma

- Infection

- Inflammation and clogging of the breast ducts

- Noncancerous pituitary tumors

- Small growth in the breast that is usually not cancer

- Severe underactive thyroid gland (hypothyroidism)

- Fibrocystic breast (normal lumpiness in the breast)

- Use of certain medicines

- Use of certain herbs, such as anise and fennel

- Widening of the milk ducts

- Intraductal pipilloma

- Subareolar abscess

- Mammary duct ectasia

- Pituitary tumor

Sometimes, babies can have nipple discharge. This is caused by hormones from the mother before birth. It usually goes away in 2 weeks. Cancers such as Paget disease (a rare type of cancer involving the skin of the nipple) can also cause nipple discharge.

Nipple discharge that is NOT normal is bloody, comes from only one nipple, or comes out on its own without squeezing or touching the nipple. Nipple discharge is more likely to be normal if it comes out of both nipples or happens when the nipple is squeezed. Squeezing the nipple to check for discharge can make it worse. Leaving the nipple alone may make the discharge stop.

The term nonpuerperal mastitis describes inflammatory lesions of the breast (mastitis) that occur unrelated to pregnancy and breastfeeding.

It is sometimes equated with duct ectasia, but other forms can be described.

The specific causes of DCIS are still unknown. The risk factors for developing this condition are similar to those for invasive breast cancer.

Some women are however more prone than others to developing DCIS. Women considered at higher risks are those who have a family history of breast cancer, those who have had their periods at an early age or who have had a late menopause. Also, women who have never had children or had them late in life are also more likely to get this condition.

Long-term use of estrogen-progestin hormone replacement therapy (HRT) for more than five years after menopause, genetic mutations (BRCA1 or BRCA2 genes), atypical hyperplasia, as well as radiation exposure or exposure to certain chemicals may also contribute in the development of the condition. Nonetheless, the risk of developing noninvasive cancer increases with age and it is higher in women older than 45 years.

Initially, an evaluation of malignancy is always indicated. If no abnormality is found, then a surgical duct excision may resolve the symptoms. Treatment also depends on whether single-duct or multiple-duct discharge is present, and whether the symptoms of nipple discharge are distressing to the patient. In some cases, there may be no need for any further intervention; in others, microdochectomy or a total duct excision may be appropriate. If the patient wishes to conserve the ability to breastfeed and only single-duct discharge is present, then ductoscopy or galactography should be considered in view of performing a localised duct excision. Once the cause of the nipple discharge is found, it will be treated by the health provider who will evaluate:

- Whether changing any medicine that has caused the discharge is appropriate

- Whether any lumps should be removed

- Whether some or all of the breast ducts should be removed

- If a prescription for cream to treat skin changes around the nipple will be helpful

- If medicines to treat a health condition are required

If all the tests are normal, treatment may not be necessary. A follow up mamogram mammogram and physical exam may be prescribed within 1 year.

Salivary gland atresia is congenital blockage or absence of the orifice of a major salivary gland duct or part of the duct itself.

It is a very rare condition. The submandibular salivary gland duct is usually involved, having failed to cannulate during embryological development. The condition first becomes apparent in the first few days after birth where a submandibular swelling caused by a retention cyst is noticed.

Vaginal adenosis is characterised by the presence of metaplastic cervical or endometrial epithelium within the vaginal wall, considered as derived from Müllerian epithelium islets in later life. In women who were exposed to certain chemicals, vaginal adenosis may arise in up to 90%. Since these contraceptives were discontinued, incidence has dropped dramatically. Risk is however still present in subsequent generations due to recent exposure.

It is thought steroid hormones play a stimulatory growth in adenosis formation. Vaginal adenosis is also often observed in adenocarcinoma patients.

Some women who have pain in one or both breasts may fear breast cancer. However, breast pain is not a common symptom of cancer. The great majority of breast cancer cases do not present with symptoms of pain, though breast pain in older women is more likely to be associated with cancer.

Strictures tend to be diagnosed based on difficulty with insertion and manipulation during sialendoscopy, or by sialography or ultrasound.

Nipple adenomas most commonly occur in 30- to 40-year-old women, but can also occur in men. They can also occur at any age, including in the elderly, in adolescence, and in infants.

Vaginal adenosis is a benign abnormality in the vagina, commonly thought to be caused by intrauterine and neonatal exposure of diethylstilbestrol and other progestagens and nonsteroidal estrogens, however it has also been observed in otherwise healthy women and has been considered at times idiopathic or congenital. Postpubertal lesions have also been observed to grow . It has a rather common incidence, of about 10% of adult women.