Cancer affects approximately 1 in 1,000 pregnant women. The most common cancers found during pregnancy are the same as the most common cancers found in non-pregnant women during childbearing ages: breast cancer, cervical cancer, leukemia, lymphoma, melanoma, ovarian cancer and colorectal cancer.

Diagnosing a new cancer in a pregnant woman is difficult, in part because any symptoms are commonly assumed to be a normal discomfort associated with pregnancy. As a result, cancer is typically discovered at a somewhat later stage than average. Some imaging procedures, such as MRIs (magnetic resonance imaging), CT scans, ultrasounds and mammograms with fetal shielding are considered safe during pregnancy; some others, such as PET scans, are not.

Treatment is generally the same as for non-pregnant women. However, radiation and radioactive drugs are normally avoided during pregnancy, especially if the fetal dose might exceed 100 cGy. In some cases, some or all treatments are postponed until after birth if the cancer is diagnosed late in the pregnancy. Early deliveries are often used to advance the start of treatment. Surgery is generally safe, but pelvic surgeries during the first trimester may cause miscarriage. Some treatments, especially certain chemotherapy drugs given during the first trimester, increase the risk of birth defects and pregnancy loss (spontaneous abortions and stillbirths).

Elective abortions are not required and, for the most common forms and stages of cancer, do not improve the mother's survival. In a few instances, such as advanced uterine cancer, the pregnancy cannot be continued and in others, the patient may end the pregnancy so that she can begin aggressive chemotherapy.

Some treatments can interfere with the mother's ability to give birth vaginally or to breastfeed. Cervical cancer may require birth by Caesarean section. Radiation to the breast reduces the ability of that breast to produce milk and increases the risk of mastitis. Also, when chemotherapy is given after birth, many of the drugs appear in breast milk, which could harm the baby.

Medications can be used to prevent cancer in a few circumstances. In the general population, NSAIDs reduce the risk of colorectal cancer; however, due to cardiovascular and gastrointestinal side effects, they cause overall harm when used for prevention. Aspirin has been found to reduce the risk of death from cancer by about 7%. COX-2 inhibitors may decrease the rate of polyp formation in people with familial adenomatous polyposis; however, it is associated with the same adverse effects as NSAIDs. Daily use of tamoxifen or raloxifene reduce the risk of breast cancer in high-risk women. The benefit versus harm for 5-alpha-reductase inhibitor such as finasteride is not clear.

Vitamin supplementation does not appear to be effective at preventing cancer. While low blood levels of vitamin D are correlated with increased cancer risk, whether this relationship is causal and vitamin D supplementation is protective is not determined. One 2014 review found that supplements had no significant effect on cancer risk. Another 2014 review concluded that vitamin D may decrease the risk of death from cancer (one fewer death in 150 people treated over 5 years), but concerns with the quality of the data were noted.

Beta-carotene supplementation increases lung cancer rates in those who are high risk. Folic acid supplementation is not effective in preventing colon cancer and may increase colon polyps. It is unclear if selenium supplementation has an effect.

Women may reduce their risk of breast cancer by maintaining a healthy weight, drinking less alcohol, being physically active and breastfeeding their children. These modifications might prevent 38% of breast cancers in the US, 42% in the UK, 28% in Brazil and 20% in China. The benefits with moderate exercise such as brisk walking are seen at all age groups including postmenopausal women. High levels of physical activity reduce the risk of breast cancer by about 14%. Strategies that encourage regular physical activity and reduce obesity could also have other benefits, such as reduced risks of cardiovascular disease and diabetes.

High intake of citrus fruit has been associated with a 10% reduction in the risk of breast cancer.

Marine omega-3 polyunsaturated fatty acids appear to reduce the risk. High consumption of soy-based foods may reduce risk.

There are different opinions on the best treatment of DCIS. Surgical removal, with or without additional radiation therapy or tamoxifen, is the recommended treatment for DCIS by the National Cancer Institute. Surgery may be either a breast-conserving lumpectomy or a mastectomy (complete or partial removal of the affected breast). If a lumpectomy is used it is often combined with radiation therapy. Tamoxifen may be used as hormonal therapy if the cells show estrogen receptor positivity. Chemotherapy is not needed for DCIS since the disease is noninvasive.

While surgery reduces the risk of subsequent cancer, many people never develop cancer even without treatment and there associated side effects. There is no evidence comparing surgery with watchful waiting and some feel watchful waiting may be a reasonable option in certain cases.

Breast cancers occur during pregnancy at the same rate as breast cancers in non-pregnant women of the same age. Breast cancer then becomes more common in the 5 or 10 years following pregnancy but then becomes less common than among the general population. These cancers are known as postpartum breast cancer and have worse outcomes including an increased risk of distant spread of disease and mortality. Other cancers found during or shortly after pregnancy appear at approximately the same rate as other cancers in women of a similar age.

Diagnosing new cancer in a pregnant woman is difficult, in part because any symptoms are commonly assumed to be a normal discomfort associated with pregnancy. As a result, cancer is typically discovered at a somewhat later stage than average in many pregnant or recently pregnant women. Some imaging procedures, such as MRIs (magnetic resonance imaging), CT scans, ultrasounds, and mammograms with fetal shielding are considered safe during pregnancy; some others, such as PET scans are not.

Treatment is generally the same as for non-pregnant women. However, radiation is normally avoided during pregnancy, especially if the fetal dose might exceed 100 cGy. In some cases, some or all treatments are postponed until after birth if the cancer is diagnosed late in the pregnancy. Early deliveries to speed the start of treatment are not uncommon. Surgery is generally considered safe during pregnancy, but some other treatments, especially certain chemotherapy drugs given during the first trimester, increase the risk of birth defects and pregnancy loss (spontaneous abortions and stillbirths). Elective abortions are not required and do not improve the likelihood of the mother surviving or being cured.

Radiation treatments may interfere with the mother's ability to breastfeed her baby because it reduces the ability of that breast to produce milk and increases the risk of mastitis. Also, when chemotherapy is being given after birth, many of the drugs pass through breast milk to the baby, which could harm the baby.

Regarding future pregnancy among breast cancer survivors, there is often fear of cancer recurrence. On the other hand, many still regard pregnancy and parenthood to represent normalcy, happiness and life fulfillment.

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.

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.

Use of radiation therapy after lumpectomy provides equivalent survival rates to mastectomy, although there is a slightly higher risk of recurrent disease in the same breast in the form of further DCIS or invasive breast cancer. Systematic reviews (including a Cochrane review) indicate that the addition of radiation therapy to lumpectomy reduces recurrence of DCIS or later onset of invasive breast cancer in comparison with breast-conserving surgery alone, without affecting mortality. The Cochrane review did not find any evidence that the radiation therapy had any long-term toxic effects. While the authors caution that longer follow-up will be required before a definitive conclusion can be reached regarding long-term toxicity, they point out that ongoing technical improvements should further restrict radiation exposure in healthy tissues. They do recommend that comprehensive information on potential side effects is given to women who receive this treatment. The addition of radiation therapy to lumpectomy appears to reduce the risk of local recurrence to approximately 12%, of which approximately half will be DCIS and half will be invasive breast cancer; the risk of recurrence is 1% for women undergoing mastectomy.

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.

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.

Invasive lobular carcinoma accounts for 5-10% of invasive breast cancer.

The histologic patterns include:

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

Loss of E-cadherin is common in lobular carcinoma but is also seen in other breast cancers.

Treatment includes surgery and adjuvant therapy.

Since Krukenberg tumors are secondary (metastatic), management might logically be driven by identifying and treating the primary cancer. The optimal treatment of Krukenberg tumors is unclear. The role of surgical resection has not been adequately addressed but if metastasis is limited to the ovaries, surgery may improve survival. The role of chemotherapy and/or radiotherapy is uncertain but may sometimes be beneficial.

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.

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.

Treatment of invasive carcinoma of no special type (NST) depends on the size of the mass (size of the tumor measured in its longest direction):

- <4 cm mass: surgery to remove the main tumor mass and to sample the lymph nodes in the axilla. The stage of the tumor is ascertained after this first surgery. Adjuvant therapy (i.e., treatment after surgery) may include a combination of chemotherapy, radiotherapy, hormonal therapy (e.g., tamoxifen) and/or targeted therapy (e.g., trastuzumab). More surgery is occasionally needed to complete the removal of the initial tumor or to remove recurrences.

- 4 cm or larger mass: modified (a less aggressive form of radical mastectomy) radical mastectomy (because any malignant mass in excess of 4 cm in size exceeds the criteria for a lumpectomy) along with sampling of the lymph nodes in the axilla.

The treatment options offered to an individual patient are determined by the form, stage and location of the cancer, and also by the age, history of prior disease and general health of the patient. Not all patients are treated the same way.

Treatment largely follows patterns that have been set for the management of postmenopausal breast cancer. The initial treatment is surgical and consists of a modified radical mastectomy with axillary dissection or lumpectomy and radiation therapy with similar treatment results as in females. Also, mastectomy with sentinel lymph node biopsy is a treatment option. In males with node-negative tumors, adjuvant therapy is applied under the same considerations as in females with node-negative breast cancer. Similarly, with node-positive tumors, males increase survival using the same adjuvants as affected females, namely both chemotherapy plus tamoxifen and other hormonal therapy. There are no controlled studies in males comparing adjuvant options. In the vast majority of males with breast cancer hormone receptor studies are positive, and those situations are typically treated with hormonal therapy.

Locally recurrent disease is treated with surgical excision or radiation therapy combined with chemotherapy. Distant metastases are treated with hormonal therapy, chemotherapy, or a combination of both. Bones can be affected either by metastasis or weakened from hormonal therapy; bisphosphonates and calcitonin may be used to counterbalance this process and strengthen bones.

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.

Chemotherapeutic options include:

- Cyclophosphamide plus methotrexate plus fluorouracil (CMF).

- Cyclophosphamide plus doxorubicin plus fluorouracil (CAF).

- Trastuzumab (monoclonal antibody therapy).

Hormonal options include:

- Orchiectomy.

- Gonadotropin hormone releasing hormone agonist (GNRH agonist) with or without total androgen blockage (anti-androgen).

- Tamoxifen for estrogen receptor–positive patients.

- Progesterone.

- Aromatase inhibitors.

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.

Some patients with metastatic breast cancer opt to try alternative therapies such as vitamin therapy, homeopathic treatments, a macrobiotic diet, chiropractic or acupuncture. There is no evidence that any of these therapies are effective; they may be harmful, either because patients pass up effective conventional therapies such as chemotherapy or anti-estrogen therapy in favor of alternative treatments, or because the treatments themselves are harmful (as in the case of apricot-pit therapy—which exposes the patient to cyanide—or in chiropractic, which can be dangerous to patients with cancer metastatic to the spinal bones or spinal cord. A macrobiotic diet is neither effective nor safe as it could hypothetically induce weight loss due to severe dietary restriction. There is limited evidence that acupuncture might relive pain in cancer patients, but data so far is insufficient to recommend its use outside of clinical trials.

There is free peer support and an online platform to interact with others going through various therapies, including Abraxane.

Treatment of metastatic breast cancer is currently an active area of research. Several medications are in development or in phase I/II trials. Typically new medications and treatments are first tested in metastatic cancer before trials in primary cancer are attempted.

Another area of research is finding combination treatments which provide higher efficacy with reduced toxicity and side effects.

Experimental medications:

- sorafenib a combined Tyrosine protein kinases inhibitor.

Although metastasis is widely accepted to be the result of the tumor cells migration, there is a hypothesis saying that some metastases are the result of inflammatory processes by abnormal immune cells. The existence of metastatic cancers in the absence of primary tumors also suggests that metastasis is not always caused by malignant cells that leave primary tumors.

Carcinoma "in situ" is, by definition, a localized phenomenon, with no potential for metastasis unless it progresses into cancer. Therefore, its removal eliminates the risk of subsequent progression into a life-threatening condition.

Some forms of CIS (e.g., colon polyps and polypoid tumours of the bladder) can be removed using an endoscope, without conventional surgical resection. Dysplasia of the uterine cervix is removed by excision (cutting it out) or by burning with a laser. Bowen's disease of the skin is removed by excision. Other forms require major surgery, the best known being intraductal carcinoma of the breast (also treated with radiotherapy). One of the most dangerous forms of CIS is the "pneumonic form" of BAC of the lung, which can require extensive surgical removal of large parts of the lung. When too large, it often cannot be completely removed, with eventual disease progression and death of the patient.

Surgery has traditionally played a limited role in the treatment of IBC because it is considered essentially a systemic cancer. However, the role of surgical intervention is being reevaluated and is now considered to be an important part of the overall treatment process. The standard treatment for newly diagnosed inflammatory breast cancer is to receive systemic therapy prior to surgery. Achieving no disease in the surgical samples gives the best prognosis. Surgery is modified radical mastectomy. Lumpectomy, segmentectomy, or skin sparing mastectomy is not recommended. Immediate reconstruction is not recommended. Upfront surgery is contraindicated. After surgery, all cases are recommended for radiation therapy unless it is contraindicated.

Because the aggressive nature of the disease, it is highly recommended to be seen by IBC specialist by a multidisciplinary team.

Further, it is critical to seek novel targeted therapy in a clinical trial setting. Three modalities, surgery, chemotherapy, and radiation are under-utilized in the USA. Estrogen and Progesterone receptor positive cases have not shown to have a better prognosis. Pathological complete response to preoperative chemotherapy imparts a more favorable prognosis than a pathologically incomplete response. Loss of heterozygosity and extensive breast inflammation upon first clinical examination have a significantly worse prognosis. Premenopausal cases have significantly worse prognosis. In postmenopausal cases lean women have significantly better prognosis than obese women. Among patients with distant metastasis at diagnosis (stage IV disease), The overall survival (OS) is worse in patients with IBC than in those with non-IBC.

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.