LCIS (lobular neoplasia is considered pre-cancerous) is an indicator (marker) identifying women with an increased risk of developing invasive breast cancer. This risk extends more than 20 years. Most of the risk relates to subsequent invasive ductal carcinoma rather than to invasive lobular carcinoma.

While older studies have shown that the increased risk is equal for both breasts, a more recent study suggests that the ipsilateral (same side) breast may be at greater risk.

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.

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.

Uterine sarcoma are rare, out of all malignancies of the uterine body only about 4% will be uterine sarcomas. Generally, the cause of the lesion is not known, however patients with a history of pelvic radiation are at higher risk. Most tumors occur after menopause.

Women who take long-term tamoxifen are at higher risk.

It occurs in all adult age groups. While the majority of patients are between 40 and 59 years old, age predilection is much less pronounced than in noninflammatory breast cancer. The overall rate is 1.3 cases per 100000, black women (1.6) have the highest rate, Asian and Pacific Islander women the lowest (0.7) rates.

Most known breast cancer risk predictors do not apply for inflammatory breast cancer. It may be slightly associated with cumulative breast-feeding duration.

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.

80% of cases in the United States are diagnosed by mammography screening.

Triple-negative breast cancer accounts for approximately 15%-25% of all breast cancer cases. The overall proportion of TNBC is very similar in all age groups. Younger women have a higher rate of basal or BRCA related TNBC while older women have a higher proportion of apocrine, normal-like and rare subtypes including neuroendocrine TNBC.

Among younger women, African American and Hispanic women have a higher risk of TNBC, with African Americans facing worse prognosis than other ethnic groups.

In 2009, a case-control study of 187 triple-negative breast cancer patients described a 2.5 increased risk for triple-negative breast cancer in women who used oral contraceptives (OCs) for more than one year compared to women who used OCs for less than one year or never. The increased risk for triple-negative breast cancer was 4.2 among women 40 years of age or younger who used OCs for more than one year, while there was no increased risk for women between the ages of 41 and 45. Also, as duration of OC use increased, triple-negative breast cancer risk increased.

In some population studies moderate alcohol consumption is associated with increase the breast cancer risk.

In contrast, research by the Danish National Institute for Public Health, comprising 13,074 women aged 20 to 91 years, found that moderate drinking had virtually no effect on breast cancer risk.

Studies that control for screening incidence show no association with moderate drinking and breast cancer, e.g.. Moderate drinkers tend to screen more which results in more diagnoses of breast cancer, including mis-diagnoses. A recent study of 23 years of breast cancer screening in the Netherlands concluded that 50% of diagnoses were over-diagnoses.

A meta analysis of cohort studies of alcohol consumption and breast cancer mortality showed no association between alcohol consumption before or after breast cancer diagnosis and recurrence after treatment.

While cancer is generally considered a disease of old age, children can also develop cancer. In contrast to adults, carcinomas are exceptionally rare in children..

The two biggest risk factors for ovarian carcinoma are age and family history.

LCIS may be treated with close clinical follow-up and mammographic screening, tamoxifen or related hormone controlling drugs to reduce the risk of developing cancer, or bilateral prophylactic mastectomy. Some surgeons consider bilateral prophylactic mastectomy to be overly aggressive treatment except for certain high-risk cases.

The relative risk of breast cancer based on a median follow-up of 8 years, in a case control study of US registered nurses, is 3.7.

A number of genes are associated with HBOC. The most common of the known causes of HBOC are:

- BRCA mutations: Harmful mutations in the "BRCA1" and "BRCA2" genes can produce very high rates of breast and ovarian cancer, as well as increased rates of other cancers.

Other identified genes include:

- "TP53": Mutations cause Li-Fraumeni syndrome. It produces particularly high rates of breast cancer among younger women with mutated genes, and despite being rare, 4% of women with breast cancer under age 30 have a mutation in this gene.

- "PTEN": Mutations cause Cowden syndrome, which produces hamartomas (benign polyps) in the colon, skin growths, and other clinical signs, as well as an increased risk for many cancers.

- "CDH1": Mutations are associated with lobular breast cancer and gastric cancer.

- "STK11": Mutations produce Peutz–Jeghers syndrome. It is extremely rare, and creates a predisposition to breast cancer, intestinal cancer, and pancreatic cancer.

- "CHEK2": Approximately one out of 40 northern Europeans have a mutation in this gene, making it a common mutation. Considered a moderate-risk mutation, it may double or triple the carrier's lifetime risk of breast cancer, and also increase the risk of colon cancer and prostate cancer.

- "ATM": Mutations cause ataxia telangectasia; female carriers have approximately double the normal risk of developing breast cancer.

- "PALB2": Studies vary in their estimate of the risk from mutations in this gene. It may be moderate risk, or as high as "BRCA2".

Approximately 45% of HBOC cases involve unidentified genes, or multiple genes.

About one percent of breast cancer develops in males. It is estimated that about 2,140 new cases are diagnosed annually in the United States (US) and about 300 in the United Kingdom (UK). The number of annual deaths in the US is about 440 (for 2016 "but fairly stable over the last 30 years"). In a study from India, eight out of 1,200 (0.7%) male cancer diagnoses in a pathology review represented breast cancer. Incidence of male breast cancer has been increasing which raises the probability of other family members developing the disease. The relative risk of breast cancer for a female with an affected brother is approximately 30% higher than for a female with an affected sister. The tumor can occur over a wide age range, but typically appears in males in their sixties and seventies.

Known risk factors include radiation exposure, exposure to female hormones (estrogen), and genetic factors. High estrogen exposure may occur by medications, obesity, or liver disease, and genetic links include a high prevalence of female breast cancer in close relatives. Chronic alcoholism has been linked to male breast cancer. The highest risk for male breast cancer is carried by males with Klinefelter syndrome. Male BRCA mutation carriers are thought to be at higher risk for breast cancer as well, with roughly 10% of male breast cancer cases carrying BRCA2 mutations, and BRCA1 mutation being in the minority.

Carcinosarcomas are malignant tumors that consist of a mixture of carcinoma (or epithelial cancer) and sarcoma (or mesenchymal/connective tissue cancer). Carcinosarcomas are rare tumors, and can arise in diverse organs, such as the skin, salivary glands, lungs, the esophagus, pancreas, colon, uterus and ovaries.

Four main hypotheses have been proposed for the cellular origins of carcinosarcoma, based largely on the pathology of the disease. First, the collision tumor hypothesis, which proposes the collision of two independent tumors resulting in a single neoplasm, based on the observation that skin cancers and superficial malignant fibrous histiocytomas are commonly seen in patients with sun-damaged skin; second, the composition hypothesis, which suggests that the mesenchymal component represents a pseudosarcomatous reaction to the epithelial malignancy; third, the combination hypothesis, which suggests that both the epithelial and mesenchymal components of the tumor arise from a common pluripotential stem cell that undergoes divergent differentiation; and fourth, the conversion/divergence hypothesis, which argues that the sarcomatous component of the tumor represents a metaplastic sarcomatous transformation of the epithelial component. Despite the remaining uncertainty on the mechanisms that generate these tumors, recent immunohistochemical, ultrastructural, and molecular genetic studies suggest and favor the notion of monoclonality in carcinosarcoma. In addition, identical p53 and KRAS mutations have been identified in both epithelial and mesenchymal components of carcinosarcoma, findings that suggest an early alteration in the histogenesis of the tumor with late transformation or degeneration of the epithelial component into the sarcomatous component.

An adenomyoepithelioma of the breast, also adenomyoepithelioma, is a rare tumour in the breast composed of glandular elements (adeno-) and myoepithelial cells. It is usually benign; however, there are reports of malignant behaviour.

The histomorphologic appearance can mimic invasive ductal carcinoma, the most common type of invasive breast cancer.

Atypical ductal hyperplasia, abbreviated ADH, is the term used for a benign lesion of the breast that indicates an increased risk of breast cancer.

The name of the entity is descriptive of the lesion; ADH is characterized by cellular proliferation (hyperplasia) within one or two breast ducts and (histomorphologic) architectural abnormalities, i.e. the cells are arranged in an abnormal or atypical way.

In the context of a core (needle) biopsy, ADH is considered an indication for a breast lumpectomy, also known as a surgical (excisional) biopsy, to exclude the presence of breast cancer.

The prognosis is determined primarily by the cancer stage. Most tumours are discovered at an early stage and have a good prognosis, especially when compared to uterine carcinosarcoma. Five year survival for stage I and stage III tumours is approximately 80% and 50% respectively.

One known cause of triple negative breast cancer is germline mutations. These are alterations within the heritable lineage that is being passed down to the offspring. 15% of TNBC can be traced back to germline mutations that are within the BRCA1 and BRCA2 genes (Song 2014). These genes were identified as high risk for triple negative due to their high predisposition for cancers of the breasts, ovaries, pancreas, and prostate (Pruss 2014). Changes or mutations in 19p13.1 and MDM4 loci have also been associated with triple negative breast cancer, but not other forms of breast cancer, thus triple negative tumors may be distinguished from other breast cancer subtypes by a unique pattern of common and rare germline alterations (Kristen 2013).

Age distribution and relation to breastfeeding duration is suggestive of some sort of involvement of hormones in the aetiology, however significant differences exist compared to normal breast cancer.

Typically IBC shows low levels of estrogen and progesterone receptor sensitivity, corresponding with poor outcome. In cases with positive estrogen receptor status antihormonal treatment is believed to improve outcome.

Paradoxically some findings suggest that especially aggressive phenotypes of IBC are characterised by high level of NF kappaB target gene expression which can be - under laboratory conditions - successfully modulated by estrogen, but not by tamoxifen.

Endometrial stromal sarcoma is a malignant subtype of endometrial stromal tumor arising from the stroma (connective tissue) of the endometrium rather than the glands. There are three grades for endometrial stromal tumors, as follows. It was previously known as "endolymphatic stromal myosis" because of diffuse infiltration of myometrial tissue or the invasion of lymphatic channels.

Carcinoma is a type of cancer that develops from epithelial cells. Specifically, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that arises from cells originating in the endodermal, mesodermal and ectodermal germ layer during embryogenesis.

Carcinomas occur when the DNA of a cell is damaged or altered and the cell begins to grow uncontrollably and become malignant. It is from the Greek καρκίνωμα 'karkinoma' meaning sore, ulcer, or cancer, itself derived from "karkinos" 'crab'.

Therapy is based on staging and patient condition and utilizes one or more of the following approaches.

Surgery is the mainstay of therapy if feasible involving total abdominal hysterectomy with bilateral salpingo-oophorectomy. Other approaches include radiation therapy, chemotherapy, and hormonal therapy.

Prognosis is relatively poor.

Sarcomatoid carcinoma is a relatively uncommon form of cancer whose malignant cells have histological, cytological, or molecular properties of both epithelial tumors ("carcinoma") and mesenchymal tumors ("sarcoma").