Breast cancer screening refers to testing otherwise-healthy women for breast cancer in an attempt to achieve an earlier diagnosis under the assumption that early detection will improve outcomes. A number of screening tests have been employed including clinical and self breast exams, mammography, genetic screening, ultrasound, and magnetic resonance imaging.

A clinical or self breast exam involves feeling the breast for lumps or other abnormalities. Clinical breast exams are performed by health care providers, while self-breast exams are performed by the person themselves. Evidence does not support the effectiveness of either type of breast exam, as by the time a lump is large enough to be found it is likely to have been growing for several years and thus soon be large enough to be found without an exam. Mammographic screening for breast cancer uses X-rays to examine the breast for any uncharacteristic masses or lumps. During a screening, the breast is compressed and a technician takes photos from multiple angles. A general mammogram takes photos of the entire breast, while a diagnostic mammogram focuses on a specific lump or area of concern.

A number of national bodies recommend breast cancer screening. For the average woman, the U.S. Preventive Services Task Force recommends mammography every two years in women between the ages of 50 and 74, the Council of Europe recommends mammography between 50 and 69 with most programs using a 2-year frequency, and in Canada screening is recommended between the ages of 50 and 74 at a frequency of 2 to 3 years. These task force reports point out that in addition to unnecessary surgery and anxiety, the risks of more frequent mammograms include a small but significant increase in breast cancer induced by radiation.

The Cochrane collaboration (2013) states that the best quality evidence neither demonstrates a reduction in cancer specific, nor a reduction in all cause mortality from screening mammography. When less rigorous trials are added to the analysis there is a reduction in mortality due to breast cancer of 0.05% (a decrease of 1 in 2000 deaths from breast cancer over 10 years or a relative decrease of 15% from breast cancer). Screening over 10 years results in a 30% increase in rates of over-diagnosis and over-treatment (3 to 14 per 1000) and more than half will have at least one falsely positive test. This has resulted in the view that it is not clear whether mammography screening does more good or harm. Cochrane states that, due to recent improvements in breast cancer treatment, and the risks of false positives from breast cancer screening leading to unnecessary treatment, "it therefore no longer seems beneficial to attend for breast cancer screening" at any age. Whether MRI as a screening method has greater harms or benefits when compared to standard mammography is not known.

Prostate cancer screening is an attempt to find unsuspected cancers. Initial screens may lead to more invasive follow-up tests such as a biopsy. Options include the digital rectal exam (DRE) and the prostate-specific antigen (PSA) blood test. Such screening is controversial and, in some people, may lead to unnecessary disruption and possibly harmful consequences. Routine screening with either a DRE or PSA is not supported by the evidence as there is no mortality benefit from screening.

The United States Preventive Services Task Force (USPSTF) recommends against the PSA test for prostate cancer screening in healthy men regardless of age. They concluded that the potential benefit of testing does not outweigh the expected harms. The Centers for Disease Control and Prevention shared that conclusion. The American Society of Clinical Oncology and the American College of Physicians discourages screening for those who are expected to live less than ten to fifteen years, while in those with a greater life expectancy a decision should be made by the person in question based on the potential risks and benefits. In general, they concluded, "it is uncertain whether the benefits associated with PSA testing for prostate cancer screening are worth the harms associated with screening and subsequent unnecessary treatment." American Urological Association (AUA 2013) guidelines call for weighing the benefits of preventing prostate cancer mortality in 1 man for every 1,000 men screened over a ten-year period against the known harms associated with diagnostic tests and treatment. The AUA recommends screening decisions in those 55 to 69 be based on shared decision making, and that if screening is performed it should occur no more often than every two years.

In those who are being regularly screened, 5-alpha-reductase inhibitor (finasteride and dutasteride) reduce the overall risk of being diagnosed with prostate cancer; however, there is insufficient data to determine if they have an effect on the risk of death and may increase the chance of more serious cases.

The selective estrogen receptor modulators (such as tamoxifen) reduce the risk of breast cancer but increase the risk of thromboembolism and endometrial cancer. There is no overall change in the risk of death. They are thus not recommended for the prevention of breast cancer in women at average risk but may be offered for those at high risk. The benefit of breast cancer reduction continues for at least five years after stopping a course of treatment with these medications.

Screening by hysteroscopy to obtain cell samples obtained for histological examination is being developed. This is similar to the current pap smear that is used to detect cervical cancer. The UK Collaborative Trial of Ovarian Cancer Screening is testing a screening technique that combines CA-125 blood tests with transvaginal ultrasound. Other studies suggest that this screening procedure may be effective. However, it's not yet clear if this approach could actually help to save lives—the full results of the trial will be published in 2015. One major problem with screening is no clear progression of the disease from stage I (noninvasive) to stage III (invasive) is seen, and it may not be possible to find cancers before they reach stage III. Another problem is that screening methods tend to find too many suspicious lesions, most of which are not cancer, but malignancy can only be assessed with surgery. The ROCA method combined with transvaginal ultrasonography is being researched in high-risk women to determine if it is a viable screening method. It is also being investigated in normal-risk women as it has shown promise in the wider population. Studies are also in progress to determine if screening helps detect cancer earlier in people with BRCA mutations.

The U.S. Preventive Services Task Force (USPSTF) issues recommendations for various cancers:

- Strongly recommends cervical cancer screening in women who are sexually active and have a cervix at least until the age of 65.

- Recommend that Americans be screened for colorectal cancer via fecal occult blood testing, sigmoidoscopy, or colonoscopy starting at age 50 until age 75.

- Evidence is insufficient to recommend for or against screening for skin cancer, oral cancer, lung cancer, or prostate cancer in men under 75.

- Routine screening is not recommended for bladder cancer, testicular cancer, ovarian cancer, pancreatic cancer, or prostate cancer.

- Recommends mammography for breast cancer screening every two years from ages 50–74, but does not recommend either breast self-examination or clinical breast examination. A 2013 Cochrane review concluded that breast cancer screening by mammography had no effect in reducing mortality because of overdiagnosis and overtreatment.

Screens for gastric cancer using photofluorography due to the high incidence there.

Research into various prognostic factors for ovarian cancer is also going on. Recent research shows that thrombocytosis predicts lower survival and higher stage cancer. Ongoing research is also investigating the benefits of surgery for recurrent ovarian cancer.

Typically self-examination leads to the detection of a lump in the breast which requires further investigation. Other less common symptoms include nipple discharge, nipple retraction. swelling of the breast, or a skin lesion such as an ulcer. Ultrasound and mammography may be used for its further definition. The lump can be examined either by a needle biopsy where a thin needle is placed into the lump to extract some tissue or by an excisional biopsy where under local anesthesia a small skin cut is made and the lump is removed. Not all palpable lesions in the male breast are cancerous, for instance a biopsy may reveal a benign fibroadenoma. In a larger study from Finland the average size of a male breast cancer lesion was 1.8 cm. Beside the histologic examination estrogen and progesterone receptor studies are performed. Further, the HER2 test is used to check for a growth factor protein. Its activity can be increased in active cancer cells and helps determine if monoclonal antibody therapy (i.e. Trastuzumab) may be useful.

Male breast cancer can recur locally after therapy, or can become metastatic.

In addition to TNM staging surgical staging for breast cancer is used; it is the same as in female breast cancer and facilitates treatment and analysis.

Routine screening of asymptomatic people is not indicated, since the disease is highly curable in its early, symptomatic stages. Instead, women, particularly menopausal women, should be aware of the symptoms and risk factors of endometrial cancer. A cervical screening test, such as a Pap smear, is not a useful diagnostic tool for endometrial cancer because the smear will be normal 50% of the time. A Pap smear can detect disease that has spread to the cervix. Results from a pelvic examination are frequently normal, especially in the early stages of disease. Changes in the size, shape or consistency of the uterus and/or its surrounding, supporting structures may exist when the disease is more advanced. Cervical stenosis, the narrowing of the cervical opening, is a sign of endometrial cancer when pus or blood is found collected in the uterus (pyometra or hematometra).

Women with Lynch syndrome should begin to have annual biopsy screening at the age of 35. Some women with Lynch syndrome elect to have a prophylactic hysterectomy and salpingo-oophorectomy to greatly reduce the risk of endometrial and ovarian cancer.

Transvaginal ultrasound to examine the endometrial thickness in women with postmenopausal bleeding is increasingly being used to aid in the diagnosis of endometrial cancer in the United States. In the United Kingdom, both an endometrial biopsy and a transvaginal ultrasound used in conjunction are the standard of care for diagnosing endometrial cancer. The homogeneity of the tissue visible on transvaginal ultrasound can help to indicate whether the thickness is cancerous. Ultrasound findings alone are not conclusive in cases of endometrial cancer, so another screening method (for example endometrial biopsy) must be used in conjunction. Other imaging studies are of limited use. CT scans are used for preoperative imaging of tumors that appear advanced on physical exam or have a high-risk subtype (at high risk of metastasis). They can also be used to investigate extrapelvic disease. An MRI can be of some use in determining if the cancer has spread to the cervix or if it is an endocervical adenocarcinoma. MRI is also useful for examining the nearby lymph nodes.

Dilation and curettage or an endometrial biopsy are used to obtain a tissue sample for histological examination. Endometrial biopsy is the less invasive option, but it may not give conclusive results every time. Hysteroscopy only shows the gross anatomy of the endometrium, which is often not indicative of cancer, and is therefore not used, unless in conjunction with a biopsy. Hysteroscopy can be used to confirm a diagnosis of cancer. New evidence shows that D&C has a higher false negative rate than endometrial biopsy.

Before treatment is begun, several other investigations are recommended. These include a chest x-ray, liver function tests, kidney function tests, and a test for levels of CA-125, a tumor marker that can be elevated in endometrial cancer.

The tumor marker CA-125 is frequently elevated in endometrial cancer and can be used to monitor response to treatment, particularly in serous cell cancer or advanced disease. Periodic MRIs or CT scans may be recommended in advanced disease and women with a history of endometrial cancer should receive more frequent pelvic examinations for the five years following treatment. Examinations conducted every three to four months are recommended for the first two years following treatment, and every six months for the next three years.

Women with endometrial cancer should not have routine surveillance imaging to monitor the cancer unless new symptoms appear or tumor markers begin rising. Imaging without these indications is discouraged because it is unlikely to detect a recurrence or improve survival, and because it has its own costs and side effects. If a recurrence is suspected, PET/CT scanning is recommended.

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.

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 screening uses medical tests to detect disease in large groups of people who have no symptoms. For individuals with high risk of developing lung cancer, computed tomography (CT) screening can detect cancer and give a person options to respond to it in a way that prolongs life. This form of screening reduces the chance of death from lung cancer by an absolute amount of 0.3% (relative amount of 20%). High risk people are those age 55–74 who have smoked equivalent amount of a pack of cigarettes daily for 30 years including time within the past 15 years.

CT screening is associated with a high rate of falsely positive tests which may result in unneeded treatment. For each true positive scan there are about 19 falsely positives scans. Other concerns include radiation exposure and the cost of testing along with follow up. Research has not found two other available tests—sputum cytology or chest radiograph (CXR) screening tests—to have any benefit.

The United States Preventive Services Task Force (USPSTF) recommends yearly screening using low-dose computed tomography in those who have a total smoking history of 30 pack-years and are between 55 and 80 years old until a person has not been smoking for more than 15 years. Screening should not be done in those with other health problems that would make treatment of lung cancer if found not an option. The English National Health Service was in 2014 re-examining the evidence for screening.

The only reliable method of diagnosis is full-thickness skin biopsy. Mammography, MRI or ultrasound often show suspicious signs; however in a significant proportion of cases they would miss a diagnosis.

Clinical presentation is typical only in 50-75% of cases; and many other conditions such as mastitis or even heart insufficiency can mimic the typical symptoms of Inflammatory Breast Cancer.

Temporary regression or fluctuation of symptoms, spontaneous or in response to conventional treatment or hormonal events should not be considered of any significance in diagnosis. Treatment with antibiotics or progesterone have been observed to cause a temporary regression of symptoms in some cases.

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.

Standard treatment is surgery with adjuvant chemotherapy and radiotherapy. As a variation, neoadjuvant chemotherapy is very frequently used for triple-negative breast cancers. This allows for a higher rate of breast-conserving surgeries and by evaluating the response to the chemotherapy gives important clues about the individual responsiveness of the particular cancer to chemotherapy.

In addition to chemotherapy, an additive called Didox can be added to aid in the reduction of drug resistance and further treatment efforts. Didox is used to inhibit ribonucleotide reductase M2 (RRM2) which contributes to the cells resistance of the chemotherapy treatment resulting in a large number of relapse (Wilson 2016). RRM2 is upregulated within these specific Triple Negative cancer cells leading to a higher rate of drug resistance and inability to slow or stop the tumor progression which leads to more aggressive forms of triple negative breast cancer that are often fatal (Wilson 2016).

TNBCs are generally very susceptible to chemotherapy. In some cases, however, early complete response does not correlate with overall survival. This makes it particularly complicated to find the optimal chemotherapy. Adding a taxane to the chemotherapy appears to improve outcome substantially.

"BRCA1"-related triple-negative breast cancer appear to be particularly susceptible to chemotherapy including platinum-based agents and taxanes.

Although mutations in single genes were not individually predictive, TNBC tumors bearing mutations in genes involved in the androgen receptor (AR) and FOXA1 pathways were much more sensitive to chemotherapy. Mutations in the AR/FOXA1 pathway provide a novel marker for identifying chemosensitive TNBC patients who may benefit from current standard-of-care chemotherapy regimens. Mutations that lowered the levels of functional BRCA1 or BRCA2 RNA were associated with significantly better survival outcomes. This BRCA deficience signature define a new, highly chemosensitive subtype of TNBC. BRCA-deficient TNBC tumors have a higher rate of clonal mutation burden, defined as more clonal tumors with a higher number of mutations per clone, and are also associated with a higher level of immune activation, which may explain their greater chemosensitivity.

In the detection of bone metastases, skeletal scintigraphy (bone scan) is very sensitive and is recommended as the first imaging study in asymptomatic individuals with suspected breast-cancer metastases. X-ray radiography is recommended if there is abnormal radionuclide uptake from the bone scan and in assessing the risk of pathological fractures, and is recommended as the initial imaging study in patients with bone pain. MRI or the combination PET-CT may be considered for cases of abnormal radionuclide uptake on bone scan, when radiography does not give an acceptably clear result.

Staging is designed to help organize the different treatment plans and to understand the prognosis better. Staging for IBC has been adapted to meet the specific characteristics of the disease. IBC is typically diagnosed in one of these stages:

- Stage IIIB - at least 1/3 of the skin of the breast is affected, and may have spread to tissues near the breast, such as the skin or chest wall, including the ribs and muscles in the chest. The cancer may have spread to lymph nodes within the breast or under the arm.

- Stage IIIC - N3 nodal involvement with an inflamed breast will upgrade the disease from Stage IIIB to Stage IIIC.

- Stage IV means that the cancer has spread to other organs. These can include the bones, lungs, liver, and/or brain.

In order to establish whether the lump is a cyst or not, several imaging tests may be performed. Mammography is usually the first imaging test to be ordered when unusual breast changes have been detected during a physical examination. A diagnostic mammography consists in a series of x-rays that provide clear images of specific areas of the breast.

Ultrasounds and MRIs are commonly performed in conjunction with mammographies as they produce clear images of the breast and clearly distinguish between fluid-filled breast cysts and solid masses. The ultrasound and MRI exams can better evaluate dense tissue of the breast; hence it is often undergone by young patients, under 30 years old.

The breast biopsy is usually the test used to confirm the suspected diagnosing. After imaging tests have been performed and have revealed unusual areas or lumps in the breast, a breast biopsy will be ordered. This test consists in removing a sample of breast tissue which is then looked at under a microscope. The specialist analyzing the tissue sample will be able to conclude if the breast changes are benign or malignant or whether breast fibrocystic disease is present.

There are four main types of breast biopsies that may be performed. A fine-needle aspiration biopsy is usually ordered when the doctor is almost certain that the lump is a cyst. This test is generally performed in conjunction with an ultrasound which is helpful in guiding the needle into a small or hard to find lump. The procedure is painless and it consists in inserting a thin needle into the breast tissue while the lump is palpated.

The core-needle biopsy is normally performed under local anesthesia and in a physician's office. The needle used in this procedure is slightly larger than the one used for a fine-needle biopsy because the procedure is intended to remove a small cylinder of tissue that will be sent to the laboratory for further examination.

A newer type of breast biopsy is the stereotactic biopsy that relies on a three-dimensional x-ray to guide the needle biopsy of non-palpable mass. The biopsy is performed in a similar manner, by using a needle to remove tissue sample but locating the specific area of the breast is done by x-raying the breast by two different angles. Surgical biopsy is a procedure performed to remove the entire lump or a part of it for laboratory analyzing. It may be painful and it is done under local anesthesia.

Clinically symptomatic CNS metastases are reported in 10–15% of patients with metastatic breast cancer; in large autopsy studies, up to 40% of women who died of metastatic breast cancer were reported to have at least one brain metastasis. CNS metastases are often viewed by patients and doctors as a late complication of metastatic breast cancer for which few effective treatments exist. In most cases, CNS involvement occurs after metastatic dissemination to the bones, liver and/or lungs has already occurred; for that reason, many patients already have refractory, terminal breast cancer by the time they are diagnosed with brain metastases. The diagnosis of brain metastases from breast cancer relies mainly on patient-reported symptoms and neuroimaging. The role of imaging in patients with suspected brain metastases is a very good modality to aid in diagnosis. According to Weil et al., 2005, neuroimaging such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) prove to be very effective in the diagnosis of brain and central nervous system metastases.

Symptoms of brain metastases from breast cancer are:

- new-onset headache

- changes in mental status, cognition and behavior

- ataxia

- cranial neuropathy, which may cause diplopia and Bell's palsy

- vomiting and nausea

- deficits in sensation, motor function, and speech

Of all brain-metastatic patients, those with a controlled extra-cranial tumor, age less than 65 years and a favorable general performance (Karnofsky performance status ≥70) fare best; older patients with a Karnofsky performance status below 70 do poorly. Effective treatments for brain metastases from breast cancer exist, although symptomatic therapy alone may be chosen for those with poor performance status. Corticosteroids are crucial to the treatment of brain metastases from any source (including the breast), and are effective in reducing peri-tumoral edema and providing symptomatic relief. Chemotherapy has not been found to be effective in the treatment of brain metastases from breast cancer, due to the inability of most chemotheraputic agents to penetrate the blood–brain barrier. Whole-brain radiation may provide a median survival of 4 to 5 months, which can be further extended by months with stereotactic surgery. Several non-randomized studies have suggested that stereotactic surgery may provide a nearly equivalent outcome, compared with surgery followed by whole brain-irradiation. Surgery tends to reduce symptoms quickly and prolong life, with an improved quality of life. Multiple metastases (up to three) may be removed surgically with a risk similar to that of a single lesion, providing similar benefits. Adjuvant radiotherapy follows surgical resection; this combined approach has been shown to prolong median survival up to 12 months, depending on the factors noted above. There is evidence that surgery may be useful in select patients with recurrent brain metastases. Mean survival from diagnosis of a brain metastasis varies between studies, ranging from 2 to 16 months (depending on involvement of the CNS, the extent of the extra-cranial metastatic disease, and the treatment applied). The mean 1-year survival is estimated at 20%. Improvements in the treatment of brain metastases are clearly needed.

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

The long-term use of supplemental vitamin A, vitamin C, vitamin D or vitamin E does not reduce the risk of lung cancer. Some studies suggest that people who eat diets with a higher proportion of vegetables and fruit tend to have a lower risk, but this may be due to confounding—with the lower risk actually due to the association of a high fruit/vegetables diet with less smoking. Several rigorous studies have not demonstrated a clear association between diet and lung cancer risk, although meta-analysis that accounts for smoking status may show benefit from a healthy diet.