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.

Industrialized nations, with the exception of Japan, have high rates of epithelial ovarian cancer, which may be due to diet in those countries. Caucasian are at a 30–40% higher risk for ovarian cancer when compared to Black and Hispanic people, likely due to socioeconomic factors; white women tend to have fewer children and different rates of gynecologic surgeries that affect risk for ovarian cancer.

Cohort studies have found a correlation between dairy consumption and ovarian cancer, but case-control studies do not show this correlation. There is mixed evidence regarding the effect of red meat and processed meat in ovarian cancer.

Tentative evidence suggests that talc, pesticides, and herbicides increase the risk of ovarian cancer. The American Cancer Society notes that as of now, no study has been able to accurately link any single chemical in the environment, or in the human diet, directly to mutations that cause ovarian cancer.

Alcohol consumption does not appear to be related to ovarian cancer. Other factors that have been investigated, such as smoking, low levels of vitamin D in the blood, presence of inclusion ovarian cysts, and infection with human papilloma virus (the cause of some cases of cervical cancer), have been disproven as risk factors for ovarian cancer. The carcinogenicity of perineal talc is controversial, because it can act as an irritant if it travels through the reproductive tract to the ovaries. Case-control studies have shown that use of perineal talc does increase the risk of ovarian cancer, but using talc more often does not create a greater risk. Use of talc elsewhere on the body is unrelated to ovarian cancer. Sitting regularly for prolonged periods is associated with higher mortality from epithelial ovarian cancer. The risk is not negated by regular exercise, though it is lowered.

Increased age (up to the 70s) is a risk factor for epithelial ovarian cancer because more mutations in cells can accumulate and eventually cause cancer. Those over 80 are at slightly lower risk.

Smoking tobacco is associated with a higher risk of mucinous ovarian cancer; after smoking cessation, the risk eventually returns to normal.A diet high in animal fats may be associated with ovarian cancer, but the connection is unclear. Diet seems to play a very small role, if any, in ovarian cancer risk.

Higher levels of C-reactive protein are associated with a higher risk of developing ovarian cancer.

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.

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

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.

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.

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.

Cancer prevention is defined as active measures to decrease cancer risk. The vast majority of cancer cases are due to environmental risk factors. Many of these environmental factors are controllable lifestyle choices. Thus, cancer is generally preventable. Between 70% and 90% of common cancers are due to environmental factors and therefore potentially preventable.

Greater than 30% of cancer deaths could be prevented by avoiding risk factors including: tobacco, excess weight/obesity, poor diet, physical inactivity, alcohol, sexually transmitted infections and air pollution. Not all environmental causes are controllable, such as naturally occurring background radiation and cancers caused through hereditary genetic disorders and thus are not preventable via personal behavior.

Tubal cancer is thought to be a relatively rare primary cancer among women accounting for 1 to 2 percent of all gynecologic cancers, In the USA tubal cancer had an incidence of 0.41 per 100,000 women from 1998 to 2003. Demographic distribution is similar to ovarian cancer, and the highest incidence was found in white, non-Hispanic women and women aged 60–79. However, recent evidence suggests tubal cancer to be much more frequent .

Evidence is accumulating that individuals with mutations of BRCA1 and BRCA2 are at higher risks for the development of PFTC.

Accurate incidence statistics on MCACL are unavailable. It is a very rare tumor, with only a few dozen cases reported in the literature to date.

In the few cases described in the literature to date, the male-to-female ratio is approximately unity, and right lung lesions occurred twice as commonly as left lung lesions. Approximately 2/3 of cases have been associated with tobacco smoking. Cases have been reported in patients as young as 29.

Most people with cancer of unknown primary origin have widely disseminated and incurable disease, although a few can be cured through treatment. With treatment, typical survival with CUP ranges from 6 to 16 months. Survival rates are lower in cases with visceral metastatic disease, ranging from 6 to 9 months. Survival rates are higher when the cancer is more limited to lymph nodes, pleura, or peritoneal metastasis, which ranges from 14 to 16 months. Long-term prognosis is somewhat better if a particular source of cancer is strongly suggested by clinical evidence.

MCACL has a much more favorable prognosis than most other forms of adenocarcinoma and most other NSCLC's. Cases have been documented of continued growth of these lesions over a period of 10 years without symptoms or metastasis. The overall mortality rate appears to be somewhere in the vicinity of 18% to 27%, depending on the criteria that are used to define this entity.

Krukenberg tumors can be seen in all age groups, with an average age of 45 years. In most countries, cancer that has metastasized to the ovary accounts for only about 1 to 2% of ovarian cancer; in the remainder, the ovary itself is the primary cancer site. However, in Japan they represent a much higher percentage of malignancies in the ovary (almost 20%) due to the increased prevalence of gastric cancer.

Krukenberg tumors account for about 15% of metastatic cancers that initially appear to have arisen in the ovary, and as such is less common than metastasis arising from ovarian epithelial and germ-cell tumors.

In people who have had nongynecologic malignancy, approximately 20% of adnexal masses are malignant, and 60% of these are Krukenberg tumors.

Primary signet ring cell carcinoma of the colon and rectum (PSRCCR) is rare, with a reported incidence of less than 1 percent. It has a poor prognosis because symptoms often develop late and it is usually diagnosed at an advanced stage. Five-year survival rates in previous studies ranged from nine to 30 percent. Average survival was between 20 and 45 months. It tends to affect younger adults with higher likelihood of lymphovascular invasion. It is worth noting that the overall survival rate of patients with SRCC was significantly poorer than that of patients with mucinous or poorly differentiated adenocarcinoma.

In advanced gastric cancers, the prognosis for patients with the SRCCs was significantly worse than for the other histological types, which can be explained by the finding that advanced SRCC gastric cancers have a larger tumor size, more lymph node metastasis, a deeper invasive depth and more Borrmann type 4 lesions than other types.

CUP sometimes runs in families. It has been associated with familial lung, kidney, and colorectal cancers, which suggests that these sites may often be the origin of unidentifiable CUP cancers.

Primary signet-ring cell carcinoma of the urinary bladder is extremely rare and patient survival is very poor and occurs mainly in men ages 38 to 83. However, one such patient treated with a radical cystectomy followed by combined S-1 and Cisplatin adjuvant chemotherapy did demonstrate promising long-term survival of 90 months.

Invasive carcinoma of no special type (NST) also known as invasive ductal carcinoma or ductal NOS and previously known as invasive ductal carcinoma, not otherwise specified (NOS) is a group of breast cancers that do not have the "specific differentiating features". Those that have these features belong to other types.

In this group are: pleomorphic carcinoma, carcinoma with osteoclast-like stromal giant cells, carcinoma with choriocarcinomatous features, and carcinoma with melanotic features. It is a diagnosis of exclusion, which means that for the diagnosis to be made all the other specific types must be ruled out.

Phyllodes tumors are considered to be on a spectrum of disease that consists of fibroadenoma, fibroadenoma variant and benign phyllodes. Some would extend the spectrum to include malignant phyllodes tumors and frank sarcoma.

Up to 10% of invasive cancers are related to radiation exposure, including both ionizing radiation and non-ionizing ultraviolet radiation. Additionally, the majority of non-invasive cancers are non-melanoma skin cancers caused by non-ionizing ultraviolet radiation, mostly from sunlight. Sources of ionizing radiation include medical imaging and radon gas.

Ionizing radiation is not a particularly strong mutagen. Residential exposure to radon gas, for example, has similar cancer risks as passive smoking. Radiation is a more potent source of cancer when combined with other cancer-causing agents, such as radon plus tobacco smoke. Radiation can cause cancer in most parts of the body, in all animals and at any age. Children and adolescents are twice as likely to develop radiation-induced leukemia as adults; radiation exposure before birth has ten times the effect.

Medical use of ionizing radiation is a small but growing source of radiation-induced cancers. Ionizing radiation may be used to treat other cancers, but this may, in some cases, induce a second form of cancer. It is also used in some kinds of medical imaging.

Prolonged exposure to ultraviolet radiation from the sun can lead to melanoma and other skin malignancies. Clear evidence establishes ultraviolet radiation, especially the non-ionizing medium wave UVB, as the cause of most non-melanoma skin cancers, which are the most common forms of cancer in the world.

Non-ionizing radio frequency radiation from mobile phones, electric power transmission and other similar sources have been described as a possible carcinogen by the World Health Organization's International Agency for Research on Cancer. However, studies have not found a consistent link between mobile phone radiation and cancer risk.

Prognosis depends to a large degree on the stage of the condition. In 1991 it was reported that about half of the patients with advanced stage disease survived 5 years with a surgical approach followed by cisplatinum-based chemotherapy.

EMECL is extremely rare, with only a handful of cases reported in the literature.

In the lung, two salivary gland-like carcinomas, mucoepidermoid carcinoma and adenoid cystic carcinoma, while extremely uncommon, occur far more often than does EMECL.

Most mammary tumors in rats are benign fibroadenomas, which are also the most common tumor in the rat. Less than 10 percent are adenocarcinomas. They occur in male and female rats. The tumors can be large and occur anywhere on the trunk. There is a good prognosis with surgery. Spayed rats have a decreased risk of developing mammary tumors.