Most of the women who develop DCIS do not experience any symptoms. The majority of cases (80-85%) are detected through screening mammography. The first signs and symptoms may appear if the cancer advances. Because of the lack of early symptoms, DCIS is most often detected at screening mammography.

In a few cases, DCIS may cause:

- A lump or thickening in or near the breast or under the arm

- A change in the size or shape of the breast

- Nipple discharge or nipple tenderness; the nipple may also be inverted, or pulled back into the breast

- Ridges or pitting of the breast; the skin may look like the skin of an orange

- A change in the way the skin of the breast, areola, or nipple looks or feels such as warmth, swelling, redness or scaliness.

Lobular carcinoma "in situ" (LCIS) is a condition caused by unusual cells in the lobules of the breast.

Many do not consider it cancer, but it can indicate an increased risk of future cancer. The national database registrars, however, consider it a malignancy.

Unlike ductal carcinoma "in situ" (DCIS), LCIS is not associated with calcification, and is typically an incidental finding in a biopsy performed for another reason. LCIS only accounts for about 15% of the "in situ" (ductal or lobular) breast cancers.

Ductal carcinoma in situ (DCIS), also known as intraductal carcinoma, is a pre-cancerous or non-invasive cancerous lesion of the breast. DCIS is classified as Stage 0. It rarely produces symptoms or a breast lump one can feel, and is usually detected through screening mammography.

In DCIS, abnormal cells are found in the lining of one or more milk ducts in the breast. "In situ" means "in place" and refers to the fact that the abnormal cells have not moved out of the mammary duct and into any of the surrounding tissues in the breast ("pre-cancerous" refers to the fact that it has not yet become an invasive cancer). In some cases, DCIS may become invasive and spread to other tissues, but there is no way of determining which lesions will remain stable without treatment, and which will go on to become invasive. DCIS encompasses a wide spectrum of diseases ranging from low-grade lesions that are not life-threatening to high-grade (i.e. potentially highly aggressive) lesions.

DCIS has been classified according to the architectural pattern of the cells (solid, cribriform, papillary, and micropapillary), tumor grade (high, intermediate, and low grade), and the presence or absence of comedo histology. DCIS can be detected on mammograms by examining tiny specks of calcium known as microcalcifications. Since suspicious groups of microcalcifications can appear even in the absence of DCIS, a biopsy may be necessary for diagnosis.

About 20–30% of those who do not receive treatment develop breast cancer. It is the most common type of pre-cancer in women. There is some disagreement as to whether, for statistical purposes, it should be counted as a cancer: some include DCIS when calculating breast cancer statistics while others do not.

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.

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.

Due to the diverse nature of salivary gland tumours, many different terms and classification systems have been used. Perhaps the most widely used currently is that system proposed by the World Health Organization in 2004, which classifies salivary neoplasms as primary or secondary, benign or malignant, and also by tissue of origin. This system defines five broad categories of salivary gland neoplasms:

Benign epithelial tumors

- Pleomorphic adenoma

- Warthin's tumor

- Myoepithelioma

- Basal cell adenoma

- Oncocytoma

- Canalicular adenoma

- Lymphadenoma

- "Sebaceous lymphadenoma"

- "Nonsebaceous lymphadenoma"

- Ductal papilloma

- "Inverted ductal papilloma"

- "Intraductal papilloma"

- "Sialadenoma papilliferum"

- Cystadenoma

- Malignant epithelial tumors

- Acinic cell carcinoma

- Mucoepidermoid carcinoma

- Adenoid cystic carcinoma

- Polymorphous low-grade adenocarcinoma

- Epithelial-myoepithelial carcinoma

- Clear cell carcinoma, not otherwise specified

- Basal cell adenocarcinoma

- Sebaceous carcinoma

- Sebaceous lymphadenocarcinoma

- Cystadenocarcinoma

- Low-grade cribriform cystadenocarcinoma

- Mucinous adenocarcinoma

- Oncocytic carcinoma

- Salivary duct carcinoma

- Salivary duct carcinoma, not otherwise specified

- Adenocarcinoma, not otherwise specified

- Myoepithelial carcinoma

- Carcinoma ex pleomorphic adenoma

- Mammary analogue secretory carcinoma

- Carcinosarcoma

- Metastasizing pleomorphic adenoma

- Squamous cell carcinoma

- Large cell carcinoma

- Lymphoepithelial carcinoma

- Sialoblastoma

- Soft tissue tumors

- Hemangioma

- Hematolymphoid tumors

- Hodgkin lymphoma

- Diffuse large B-cell lymphoma

- Extranodal marginal zone B cell lymphoma

- Secondary tumors (i.e. a tumor which has metastasized to the salivary gland from a distant location)

Others, not included in the WHO classification above, include:

- Intraosseous (central) salivary gland tumors

- Hybrid tumors (i.e. a tumor displaying combined forms of histologic tumor types)

- Hybrid carcinoma

- Others

- Others

- Keratocystoma

- Sialolipoma

Symptoms are very variable and may not be present at all in "occult inflammatory breast cancer". Quick onset of symptoms is typical, the breast often looks swollen and red, or “inflamed”, sometimes overnight, and are easy to misdiagnose as mastitis. Invasion of the local lymphatic ducts impairs drainage and causes edematous swelling of the breast. Because the skin of the breast is tethered by the suspensory ligament of Cooper, the accumulation of fluid may cause the skin of the breast to assume a dimpled appearance similar to an orange peel (peau d'orange). A palpable tumor is frequently not obvious as in other forms of breast cancer.

Symptoms may include:

- Sudden swelling of the breast

- Skin changes on breast

- Reddened area with texture resembling the peel of an orange (peau d’orange)

- Nipple retraction (flattened look) or discharge

- Pain in the breast

- Itching of breast

- Swelling of lymph nodes under the arm or in the neck

- Unusual warmth of the affected breast

- Breast is harder or firmer

Other symptoms may rarely include:

- Swelling of the arm

- Breast size may decrease instead of increasing

- Although a dominant mass is present in many cases, most inflammatory cancers present as diffuse infiltration of the breast without a well-defined tumor.

- A lump may become present and grow rapidly

Most patients do not experience all the symptoms of IBC. Not all symptoms need to be present in order to be diagnosed.

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.

Inflammatory breast cancer is one of the most aggressive types of breast cancer that can occur in women of any age (and,

extremely rarely, in men). It is called inflammatory because it frequently presents with symptoms resembling an inflammation. Despite the name, whether inflammation contributes to the development of "inflammatory breast cancer" remains an area of ongoing research. However it can present with very variable signs and symptoms, frequently without detectable tumors and therefore is often not detected by mammography or ultrasound.

Typical presentation is rapid swelling, sometimes associated by skin changes (peau d'orange), and nipple retraction. Other symptoms include rapid increase in breast size, redness, persistent itching, skin hot to touch. IBC often initially resembles mastitis.

Only about 50-75% cases have the typical presentation. Symptoms can be completely atypical such as acute central venous thrombosis as the sole presenting symptom.

IBC makes up only a small percentage of breast cancer cases (1-6% in the USA). IBC is often diagnosed in younger women although average age of presentation does not differ much from other kinds of breast cancer (average age 57 years). African-Americans are usually diagnosed at younger ages than Caucasian women, and also have a higher risk of getting IBC. Recent advances in therapy have improved the prognosis considerably and at least one third of women will survive the diagnosis by 10 years or longer.

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.

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'.

Radial scars are diagnosed by a microscopic examination of excised tissue, i.e. they are diagnosed by pathologists based on their histomorphology.

Histological variants of lung cancer classified as sarcomatoid carcinoma include pleomorphic carcinoma, giant cell carcinoma, spindle cell carcinoma, carcinosarcoma, and pulmonary blastoma.

ADH, generally, is asymptomatic. It usually comes to medical attention on a screening mammogram, as a non-specific suspicious abnormality that requires a biopsy.

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").

Like the cells of atypical lobular hyperplasia and invasive lobular carcinoma, the abnormal cells of LCIS consist of small cells with oval or round nuclei and small nucleoli detached from each other. Mucin-containing signet-ring cells are commonly seen. LCIS generally leaves the underlying architecture intact and recognisable as lobules. Estrogen and progesterone receptors are present and HER2/neu overexpression is absent in most cases of LCIS.

Salivary gland tumours usually present as a lump or swelling in the affected gland which may or may not have been present for a long time. The lump may be accompanied by symptoms of duct blockage (e.g. xerostomia). Usually, in their early stages it is not possible to distinguish a benign tumour from a malignant one. One of the key differentiating symptoms of a malignant growth is nerve involvement. For example signs of facial nerve damage (e.g facial palsy) are associated with malignant parotid tumours. Facial pain, and paraesthesia are also very often associated with a malignant tumours. Other red flag symptoms which may suggest malignancy and warrant further investigation are fixation of the lump to the overlying skin, ulceration and induration of the mucosa.

In breast pathology, a radial scar of the breast, formally radial scar of the breast, is a benign breast lesion that can radiologically mimic malignancy, i.e. cancer.

Radial scar is associated with atypia and/or malignancy and may be an independent risk factor for the development of carcinoma in either breast.

A malignant mixed Müllerian tumor, also known as malignant mixed mesodermal tumor, MMMT and carcinosarcoma, is a malignant neoplasm found in the uterus, the ovaries, the fallopian tubes and other parts of the body that contains both carcinomatous (epithelial tissue) and sarcomatous (connective tissue) components. It is divided into two types, homologous (in which the sarcomatous component is made of tissues found in the uterus such as endometrial, fibrous and/or smooth muscle tissues) and a heterologous type (made up of tissues not found in the uterus, such as cartilage, skeletal muscle and/or bone). MMMT account for between two and five percent of all tumors derived from the body of the uterus, and are found predominantly in postmenopausal women with an average age of 66 years. Risk factors are similar to those of adenocarcinomas and include obesity, exogenous estrogen therapies, and nulliparity. Less well-understood but potential risk factors include tamoxifen therapy and pelvic irradiation.

Male breast cancer (male breast neoplasm) is a rare cancer in males that originates from the breast. Many males with breast cancer have inherited a "BRCA" mutation, but there are other causes, including alcohol abuse and exposure to certain hormones and ionizing radiation.

As it presents a similar pathology as female breast cancer, assessment and treatment relies on experiences and guidelines that have been developed in female patients. The optimal treatment is currently not known.

Triple-negative breast cancer (sometimes abbreviated TNBC) refers to any breast cancer that does not express the genes for estrogen receptor (ER), progesterone receptor (PR) or Her2/neu. This makes it more difficult to treat since most hormone therapies target one of the three receptors, so triple-negative cancers often require combination therapies. Triple negative is sometimes used as a surrogate term for basal-like; however, more detailed classification may provide better guidance for treatment and better estimates for prognosis.

Triple-negative breast cancers comprise a very heterogeneous group of cancers. There are conflicting information over prognosis for the various subtypes but it appears that the Nottingham prognostic index is valid and hence general prognosis is rather similar with other breast cancer of same stage, except that more aggressive treatment is required. Some types of triple-negative breast cancer are known to be more aggressive with poor prognosis, while other types have very similar or better prognosis than hormone receptor positive breast cancers. Pooled data of all triple-negative subtypes suggest that with optimal treatment 20-year survival rates are very close to those of hormone positive cancer.

Triple-negative breast cancers have a relapse pattern that is very different from hormone-positive breast cancers: the risk of relapse is much higher for the first 3–5 years but drops sharply and substantially below that of hormone-positive breast cancers after that. This relapse pattern has been recognized for all types of triple-negative cancers for which sufficient data exists although the absolute relapse and survival rates differ across subtypes.

The first noticeable symptom of breast cancer is typically a lump that feels different from the rest of the breast tissue. More than 80% of breast cancer cases are discovered when the woman feels a lump. The earliest breast cancers are detected by a mammogram. Lumps found in lymph nodes located in the armpits can also indicate breast cancer.

Indications of breast cancer other than a lump may include thickening different from the other breast tissue, one breast becoming larger or lower, a nipple changing position or shape or becoming inverted, skin puckering or dimpling, a rash on or around a nipple, discharge from nipple/s, constant pain in part of the breast or armpit, and swelling beneath the armpit or around the collarbone. Pain ("mastodynia") is an unreliable tool in determining the presence or absence of breast cancer, but may be indicative of other breast health issues.

Inflammatory breast cancer is a particular type of breast cancer which can pose a substantial diagnostic challenge. Symptoms may resemble a breast inflammation and may include itching, pain, swelling, nipple inversion, warmth and redness throughout the breast, as well as an orange-peel texture to the skin referred to as "peau d'orange". As inflammatory breast cancer does not present as a lump there can sometimes be a delay in diagnosis.

Another reported symptom complex of breast cancer is Paget's disease of the breast. This syndrome presents as skin changes resembling eczema, such as redness, discoloration, or mild flaking of the nipple skin. As Paget's disease of the breast advances, symptoms may include tingling, itching, increased sensitivity, burning, and pain. There may also be discharge from the nipple. Approximately half of women diagnosed with Paget's disease of the breast also have a lump in the breast.

In rare cases, what initially appears as a fibroadenoma (hard, movable non-cancerous lump) could in fact be a phyllodes tumor. Phyllodes tumors are formed within the stroma (connective tissue) of the breast and contain glandular as well as stromal tissue. Phyllodes tumors are not staged in the usual sense; they are classified on the basis of their appearance under the microscope as benign, borderline, or malignant.

Occasionally, breast cancer presents as metastatic disease—that is, cancer that has spread beyond the original organ. The symptoms caused by metastatic breast cancer will depend on the location of metastasis. Common sites of metastasis include bone, liver, lung and brain. Unexplained weight loss can occasionally signal breast cancer, as can symptoms of fevers or chills. Bone or joint pains can sometimes be manifestations of metastatic breast cancer, as can jaundice or neurological symptoms. These symptoms are called "non-specific", meaning they could be manifestations of many other illnesses.

Most symptoms of breast disorders, including most lumps, do not turn out to represent underlying breast cancer. Fewer than 20% of lumps, for example, are cancerous, and benign breast diseases such as mastitis and fibroadenoma of the breast are more common causes of breast disorder symptoms. Nevertheless, the appearance of a new symptom should be taken seriously by both patients and their doctors, because of the possibility of an underlying breast cancer at almost any age.

The symptoms produced by metastatic breast cancer vary by the location of the metastases. For instance:

- Metastatic disease to the bone causes severe, progressive pain, and, less commonly, pathological fracture, erythema over the affected bone, and swelling.

- Metastatic breast cancer to the brain causes the following symptoms: persistent, progressively worsening headache, visual changes, seizures, nausea or vomiting, vertigo, behavioral and personality changes, and increased intracranial pressure.

- Metastatic disease to the liver causes jaundice, elevated liver enzymes, abdominal pain, loss of appetite, nausea, and vomiting

- Metastatic breast cancer to the lung or pleura causes chronic cough, dyspnea, abnormal chest X-ray, and chest pain.

- Other nonspecific systemic symptoms of metastatic breast cancer include fatigue, malaise, weight loss, and poor appetite.

Fibroadenomas, are benign breast tumours characterized by an admixture of stromal and epithelial tissue. Breasts are made of lobules (milk producing glands) and ducts (tubes that carry the milk to the nipple). These are surrounded by glandular, fibrous and fatty tissues. Fibroadenomas develop from the lobules. The glandular tissue and ducts grow over the lobule to form a solid lump.

Since both fibroadenomas, and breast lumps as a sign of breast cancer can appear similar, it is recommended to perform ultrasound analyses and possibly tissue sampling with subsequent histopathologic analysis in order to make a proper diagnosis. Unlike typical lumps from breast cancer, fibroadenomas are easy to move, with clearly defined edges.

Fibroadenomas are sometimes called breast mice or a breast mouse owing to their high mobility in the breast.

Low-grade endometrial stromal sarcoma consists of cells resembling normal proliferative phase endometrium, but with infiltration or vascular invasion. These behave less aggressively, sometimes metastasizing, with cancer stage the best predictor of survival. The cells express estrogen/progesterone-receptors.