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.

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.

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.

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.

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

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.

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.

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 the older literature survival rates have been given as 35–50% for Stage I–II and 0–15% for Stage III and IV UPSC, More recently it was reported that forty-two percent of 138 patients were found disease-free at five years.

In 2009, the journal of "Gynecologic Oncology" reported the following 5-year survival rates based upon stage of cancer:

- Stage I: 50% - 80%

- Stage II: 50%

- Stage III: 20%

- Stage IV: 5% - 10%

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.

Prognosis of the UPSC is affected by age, stage, and histology as well as treatment.

Antibodies may be used to determine the expression of protein markers on the surface of cancer cells. Often the expression of these antigens is similar to the tissue that the cancer grew from, so immunohistochemical testing sometimes helps to identify the source of the cancer. Individual tests often do not provide definitive answers, but sometimes patterns may be observed, suggesting a particular site of origin (e.g. lung, colon, etc.). Immunohistochemical testing suggests a single source of cancer origin in about one in four cases of CUP. However, there is a lack of definitive research data showing that treatment guided by information from immunohistochemical testing improves outcomes or long-term prognosis.

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.

There is no evidence that mastectomy decreases the risk of death over a lumpectomy. Mastectomy; however, may decrease the rate of the DCIS or invasive cancer occurring in the same location.

Mastectomies remain a common recommendation in those with persistent microscopic involvement of margins after local excision or with a diagnosis of DCIS and evidence of suspicious, diffuse microcalcifications. Some institutions that have encountered high rates of recurrent invasive cancers after mastectomy for DCIS have endorsed routine sentinel node biopsy (SNB). Others reserve SNB for only certain people. Most agree that SNB should be considered with tissue diagnosis of high risk DCIS (grade III with palpable mass or larger size on imaging) as well as in people undergoing mastectomy after a core or excisional biopsy diagnosis of DCIS.

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.

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.

According to the NIH Consensus Conference , if DCIS is allowed to go untreated, the natural course or natural history varies according to the grade of the DCIS. Unless treated, approximately 60 percent of low-grade DCIS lesions will have become invasive at 40 years follow-up. High-grade DCIS lesions that have been inadequately resected and not given radiotherapy have a 50 percent risk of becoming invasive breast cancer within seven years. Approximately half of low-grade DCIS detected at screening will represent overdiagnosis, but overdiagnosis of high-grade DCIS is rare. The natural history of intermediate-grade DCIS is difficult to predict. Approximately one-third of malignant calcification clusters detected at screening mammography already have an invasive focus.

The prognosis of IDC depends, in part, on its histological subtype. Mucinous, papillary, cribriform, and tubular carcinomas have longer survival, and lower recurrence rates. The prognosis of the most common form of IDC, called "IDC Not Otherwise Specified", is intermediate. Finally, some rare forms of breast cancer (e.g., sarcomatoid carcinoma, inflammatory carcinoma) have a poor prognosis. Regardless of the histological subtype, the prognosis of IDC depends also on tumor size, presence of cancer in the lymph nodes, histological grade, presence of cancer in small vessels (vascular invasion), expression of hormone receptors and of oncogenes like HER2/neu.

These parameters can be entered into models that provide a statistical probability of systemic spread. The probability of systemic spread is a key factor in determining whether radiation and chemotherapy are worthwhile. The individual parameters are important also because they can predict how well a cancer will respond to specific chemotherapy agents.

Overall, the 5-year survival rate of invasive ductal carcinoma was approximately 85% in 2003.

Treatment and survival is determined, to a great extent, by whether or not a cancer remains localized or spreads to other locations in the body. If the cancer metastasizes to other tissues or organs it usually dramatically increases a patient's likelihood of death. Some cancers—such as some forms of leukemia, a cancer of the blood, or malignancies in the brain—can kill without spreading at all.

Once a cancer has metastasized it may still be treated with radiosurgery, chemotherapy, radiation therapy, biological therapy, hormone therapy, surgery, or a combination of these interventions ("multimodal therapy"). The choice of treatment depends on a large number of factors, including the type of primary cancer, the size and location of the metastases, the patient's age and general health, and the types of treatments used previously. In patients diagnosed with CUP it is often still possible to treat the disease even when the primary tumor cannot be located.

Current treatments are rarely able to cure metastatic cancer though some tumors, such as testicular cancer and thyroid cancer, are usually curable.

Palliative care, care aimed at improving the quality of life of people with major illness, has been recommended as part of management programs for metastasis.

These aggressive tumors are generally diagnosed at advanced stages and survival is generally shorter. The prognosis of SRCC and its chemosensitivity with specific regimens are still controversial as SRCC is not specifically identified in most studies and its poor prognosis may be due to its more advanced stage. One study suggests that its dismal prognosis seems to be caused by its intrinsic tumor biology, suggesting an area for further research.

CUP is a term that refers to many different cancers. For that reason, treatment depends on where the cancer is found, the microscopic appearance of the cancer cells, the biochemical characterization of the cells, and the patient’s age and overall physical condition. In women, who present with axillary lymph node involvement, treatment is offered along the lines of breast cancer. In patients, who have neck lymph node involvement, then treatment is offered along the lines of head and neck cancer. If inguinal lymph nodes are involved, then treatment may be offered along the lines of genitourinary cancer.

If the site of origin is unknown or undiscovered, then the histology of the tumor (e.g., adenocarcinoma, squamous cell or mesenchymal) can usually be identified, and a probable origin may be assumed. When this is possible, then treatment is based on the type of cell and probable origin. Based on histological subtype, combination chemotherapy may be selected. A combination of carboplatin and paclitaxel is often used. Advances techniques such as FISH and tissue of origin testing may also be employed. Germ cell tumors often carry abnormality of chromosome 12, which if identified, directs treatment for metastatic germ cell tumors.

No method is standard for all forms of CUP, but chemotherapy, radiation therapy, hormone therapy, and surgery may be used alone or in combination to treat patients who have CUP. Even when the cancer is unlikely to be cured, treatment may help the patient live longer or improve the patient’s quality of life. Radiation may be used to shrink a variety of local tumors. However, the potential side effects of the treatment must be considered along with the potential benefits.

In CUP to secondary neck nodes, surgery followed by external beam radiotherapy is sufficient.

For CUP with an unfavorable prognosis, treatment with taxanes may provide a slight survival benefit. The uncertainties and ambiguity inherent in a CUP diagnosis may cause additional stress for the patient.

Metastasis is a complex and interconnected multi-step process. Each step in the process is a potential target for therapies to prevent or reduce metastasis. Those steps which have a good clinical window are the best targets for therapy. Each event in metastasis is highly regulated and requires a synergistic activation of different ECM proteins, growth factors and so on. Although the occasional patient with metastatic breast cancer benefits from surgical resection of an isolated metastasis and most patients receive radiotherapy (often for palliation alone) during the course of their disease, the treatment of metastatic breast carcinoma typically involves the use of systemic therapy.

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.