Neoplasm is an abnormal growth of tissue which, if it forms a mass, is commonly referred to as a tumor. This abnormal growth (neoplasia) usually but not always forms a mass.

ICD-10 classifies neoplasms into four main groups: benign neoplasms, in situ neoplasms, malignant neoplasms, and neoplasms of uncertain or unknown behavior. Malignant neoplasms are also simply known as cancers and are the focus of oncology.

Prior to the abnormal growth of tissue, as neoplasia, cells often undergo an abnormal pattern of growth, such as metaplasia or dysplasia. However, metaplasia or dysplasia does not always progress to neoplasia. The word is from Ancient Greek νέος- "neo" "new" and πλάσμα "plasma" "formation, creation".

A benign tumor is a mass of cells (tumor) that lacks the ability to invade neighboring tissue or metastasize. Benign tumors do not spread into, or invade, nearby tissues. Benign tumors can sometimes be quite large, however. When removed, they usually do not grow back, whereas malignant tumors sometimes do. Unlike most benign tumors elsewhere in the body, benign brain tumors can be life threatening. Benign tumors generally have a slower growth rate than malignant tumors and the tumor cells are usually more differentiated (cells have normal features). Benign tumors are typically surrounded by an outer surface (fibrous sheath of connective tissue) or remain with the epithelium. Common examples of benign tumors include moles and uterine fibroids.

Although benign tumors will not metastasize or locally invade tissues, some types may still produce negative health effects. The growth of benign tumors produces a "mass effect" that can compress tissues and may cause nerve damage, reduction of blood to an area of the body (ischaemia), tissue death (necrosis) and organ damage. The mass effect of tumors is more prominent if the tumor is within an enclosed space such as the cranium, respiratory tract, sinus or inside bones. Tumors of endocrine tissues may overproduce certain hormones, especially when the cells are well differentiated. Examples include thyroid adenomas and adrenocortical adenomas.

Although most benign tumors are not life-threatening, many types of benign tumors have the potential to become cancerous (malignant) through a process known as tumour progression. For this reason and other possible negative health effects, some benign tumors are removed by surgery.

A neoplasm can be benign, potentially malignant, or malignant (cancer).

- Benign tumors include uterine fibroids and melanocytic nevi (skin moles). They are circumscribed and localized and do not transform into cancer.

- Potentially-malignant neoplasms include carcinoma in situ. They are localised, do not invade and destroy but in time, may transform into a cancer.

- Malignant neoplasms are commonly called cancer. They invade and destroy the surrounding tissue, may form metastases and, if untreated or unresponsive to treatment, will prove fatal.

- Secondary neoplasm refers to any of a class of cancerous tumor that is either a metastatic offshoot of a primary tumor, or an apparently unrelated tumor that increases in frequency following certain cancer treatments such as chemotherapy or radiotherapy.

- Rarely there can be a metastatic neoplasm with no known site of the primary cancer and this is classed as a cancer of unknown primary origin

A myxoid liposarcoma is a malignant adipose tissue neoplasm of myxoid appearance histologically.

Myxoid liposarcomas are the second most common type of liposarcoma, representing 30–40% of all liposarcomas in the limbs; occurring most commonly in the legs, particularly the thigh, followed by the buttocks, retroperitoneum, trunk, ankle, proximal limb girdle, head and neck, and wrist. They occur in the intermuscular fascial planes or deep-seated areas. They present as a large, slow-growing, painless mass.

They are associated with a fusion between DDIT3 or "CHOP" (at 12q13.1-q13.2) and FUS or "TLS" (at 16p11.2) or EWS (at 22q12.2).

The specific translocation of FUS-DDIT3 is t(12;16)(q13;p11).

Benign tumors are very diverse, and may be asymptomatic or may cause specific symptoms depending on their anatomic location and tissue type. They grow outwards, producing large rounded masses, which can cause what is known as a "mass effect". This growth can cause compression of local tissues or organs, which can cause many effects such as blockage of ducts, reduced blood flow (ischaemia), tissue death (necrosis) and nerve pain or damage. Some tumors also produce hormones that can lead to life-threatening situations. Insulinomas can produce large amounts of insulin leading to hypoglycemia. Pituitary adenomas can cause elevated levels of hormones such as growth hormone and insulin-like growth factor-1, which cause acromegaly; prolactin; ACTH and cortisol, which cause Cushings disease; TSH, which causes hyperthyroidism; and FSH and LH. Bowel intussusception can occur with various benign colonic tumors. Cosmetic effects can be caused by tumors, especially those of the skin, possibly causing psychological effects on the person with the tumor. Vascular tumors can bleed, which in some cases can be substantial, leading to anemia.

An adipose tissue neoplasm is a neoplasm derived from adipose tissue.

An example is lipoma.

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'.

Adenocarcinoma (; plural adenocarcinomas or adenocarcinomata ) is a type of cancerous tumor that can occur in several parts of the body. It is defined as neoplasia of epithelial tissue that has glandular origin, glandular characteristics, or both. Adenocarcinomas are part of the larger grouping of carcinomas, but are also sometimes called by more precise terms omitting the word, where these exist. Thus invasive ductal carcinoma, the most common form of breast cancer, is adenocarcinoma but does not use the term in its name—however, esophageal adenocarcinoma does to distinguish it from the other common type of esophageal cancer, esophageal squamous cell carcinoma. Several of the most common forms of cancer are adenocarcinomas, and the various sorts of adenocarcinoma vary greatly in all their aspects, so that few useful generalizations can be made about them.

In the most specific usage (narrowest sense), the glandular origin or traits are exocrine; endocrine gland tumors, such as a VIPoma, an insulinoma, or a pheochromocytoma, are typically not referred to as adenocarcinomas but rather are often called neuroendocrine tumors. Epithelial tissue sometimes includes, but is not limited to, the surface layer of skin, glands, and a variety of other tissue that lines the cavities and organs of the body. Epithelial tissue can be derived embryologically from any of the germ layers (ectoderm, endoderm, or mesoderm). To be classified as adenocarcinoma, the cells do not necessarily need to be part of a gland, as long as they have secretory properties. Adenocarcinoma is the malignant counterpart to adenoma, which is the benign form of such tumors. Sometimes adenomas transform into adenocarcinomas, but most do not.

Well differentiated adenocarcinomas tend to resemble the glandular tissue that they are derived from, while poorly differentiated adenocarcinomas may not. By staining the cells from a biopsy, a pathologist can determine whether the tumor is an adenocarcinoma or some other type of cancer. Adenocarcinomas can arise in many tissues of the body owing to the ubiquitous nature of glands within the body, and, more fundamentally, to the potency of epithelial cells. While each gland may not be secreting the same substance, as long as there is an exocrine function to the cell, it is considered glandular and its malignant form is therefore named adenocarcinoma.

In medicine, desmoplasia is the growth of fibrous or connective tissue. It is also called desmoplastic reaction to emphasize that it is secondary to an insult. Desmoplasia may occur around a neoplasm, causing dense fibrosis around the tumor, or scar tissue (adhesions) within the abdomen after abdominal surgery.

Desmoplasia is usually only associated with malignant neoplasms, which can evoke a fibrosis response by invading healthy tissue. Invasive ductal carcinomas of the breast often have a scirrhous, stellate appearance caused by desmoplastic formations.

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.

Hypopharyngeal cancer is a disease in which malignant cells grow in the hypopharynx (the area where the larynx and esophagus meet).

It first forms in the outer layer (epithelium) of the hypopharynx (last part of the pharynx), which is split into three areas. Progression of the disease is defined by the spread of cancer into one or more areas and into deeper tissues.

This type of cancer is rare. Only about 2,500 cases are seen in the US each year. Because of this, Hypopharyngeal Cancer is difficult to catch in its earliest stages and has one of the highest mortality rates of any head and neck cancer.

As of 2004, no simple and comprehensive classification system has been devised and accepted within the scientific community. Traditionally, however, malignancies have generally been classified into various types using a combination of criteria, including:

the cell type from which they start, specifically:

1. Epithelial cells ⇨ carcinoma

2. Non-hematopoietic mesenchymal cells ⇨ sarcoma

3. Hematopoietic cells

1. bone marrow-derived cells that normally mature in the bloodstream ⇨ Leukemia

2. bone marrow-derived cells that normally mature in the lymphatic system ⇨ Lymphoma

4. Germ cells ⇨ Germinoma

Other criteria that play a role in a cancer diagnosis include:

- The degree to which the malignant cells resemble their normal, untransformed counterparts

- the appearance of the local tissue and stromal architecture

- the anatomical location from which tumors arise

- genetic, epigenetic, and molecular features

Most cancers typically present as a single primary tumor. Over the course of time—particularly if the primary tumor is left untreated—smaller "satellite" tumors will appear at other places in the body, a phenomenon known as metastasis. Less commonly, a metastatic tumor is found first; but in most such cases, the primary tumor can then be located via examination and testing. Rarely (3-5% of the time), the primary tumor cannot be found because it is too small, or because it has regressed due to immune system activity or other factors. In such situations a diagnosis of cancer of unknown primary origin (CUP) is made.

CUP usually comes to attention because of masses or swellings found somewhere in the body, either by physical examination or on medical imaging performed for another indication. The disease typically develops rapidly, and metastases may occur in places in the body that are otherwise unusual. Comprehensive physical examination is part of the process to identify a possible primary source of cancer; this should include the breasts, lymph nodes, the skin, external genitals, as well as an internal examination of the rectum and of the pelvic organs.

The location of metastases may be a clue as to the underlying source, even if this cannot be found on investigations. For instance, a woman in whom there is axillary lymphadenopathy (swelling in the lymph nodes of the armpit) it is likely that the cancer originated in the breast, and men with lymph node deposits in the mediastinum of the chest and/or retroperitoneal space of the abdomen may have a germ cell tumor.

Symptoms of Hypopharyngeal Cancer include:

- Swollen lymph nodes in the neck (first sign of a problem in half of all patients)

- Sore throat in one location that persists after treatment

- Pain that radiates from the throat to the ears

- Difficult or painful swallowing (often leads to malnutrition and weight loss because of a refusal to eat)

- Voice changes (late stage cancer)

There is debate over the naming of MMMT; the term carcinosarcoma was formerly used to describe lesions with homologous tumors, and "malignant mixed Müllerian tumor" or "mixed mesodermal tumor" was used to describe heterologous tumors. While "carcinosarcoma" now considered standard, "malignant mixed Müllerian tumor" has a lengthy history within gynecological literature and is expected to continue to be used. The naming issue to a certain extent reflects histological characteristics and development of the tumors, in which the different types of tissues are believed to either develop separately and join into a single mass (the "collision" theory), that an adenocarcinoma stimulates the stroma to create a tumor (the "composition" theory), or that the tumor is the result of a stem cell that differentiates into different cell types (the "combination" theory). "Collision" tumors are normally easily recognized and not considered true MMMTs; the "combination" theory is most widely held, and is due to evidence that the tumors develop from a single line of cells, developing in a fashion similar to the fundus of the uterus from the Müllerian duct - first from a stem cell into a population of cells, that then differentiates into epithelial and stromal components.

There is evidence that some tumors are better explained by the composition theory, due to the aggressive nature of the epithelial cells involved which tend to metastasize much more readily than the sarcomal component. The behavior of MMMT overall is more related to the type and grade of the epithelium than the sarcoma, which suggests the sarcomal portion is an atypical "bystander" than primary driver of the tumor. Despite this, when purely endometrial tumors are compared to MMMTs, the MMMT tumor tends to have a worse prognosis.

Cancer of unknown primary origin (CUP, "occult cancer") is a cancer that is determined to be at the metastatic stage at the time of diagnosis, but a primary tumor cannot be identified. A diagnosis of CUP requires a clinical picture consistent with metastatic disease and one or more biopsy results inconsistent with a primary tumor.

CUP is found in about 3 to 5% of all people diagnosed with invasive cancer, and carries a poor prognosis in most (80 to 85%) of those circumstances. The other 15 to 20% of patients, however, have a relatively long survival with appropriate treatment.

Desmoplasia originates from the Ancient Greek δεσμός "desmos", "knot", "bond" and πλάσις "plasis", "formation". It is usually used in the description of desmoplastic small round cell tumors.

Neoplasia is the medical term used for both benign and malignant tumors, and is used as a blanket term that refers to abnormal, excessive, uncoordinated, and autonomous cellular/tissue growth.

Desmoplasia refers to growth of dense connective tissue or stroma. This growth is characterized by low cellularity with hyalinized or sclerotic stroma and disorganized blood vessel infiltration. This growth is called a desmoplastic response and occurs as result of injury or neoplasia. This response is coupled with malignancy in non-cutaneous neoplasias, and with benign or malignant tumors if associated with cutaneous pathologies.

The heterogeneity of tumor cancer cells and stroma cells combined with the complexities of surrounding connective tissue suggest that understanding cancer by tumor cell genomic analysis is not sufficient; analyzing the cells together with the surrounding stromal tissue may provide more comprehensive and meaningful data.

Around 95% of penile cancers are squamous cell carcinomas. They are classified into the following types:

- basaloid (4%)

- warty (6%)

- mixed warty-basaloid (17%)

- verrucous (8%)

- papillary (7%)

- other SCC mixed (7%)

- sarcomatoid carcinomas (1%)

- not otherwise specified (49%)

Other types of carcinomas are rare and may include small cell, Merkel cell, clear cell, sebaceous cell or basal cell tumors. Non-epithelial malignancies such as melanomas and sarcomas are even more rare.

In their early stages, soft-tissue sarcomas usually do not cause symptoms. Because soft tissue is relatively elastic, tumors can grow rather large, pushing aside normal tissue, before they are felt or cause any problems. The first noticeable symptom is usually a painless lump or swelling. As the tumor grows, it may cause other symptoms, such as pain or soreness, as it presses against nearby nerves and muscles. If in the abdomen it can cause abdominal pains commonly mistaken for menstrual cramps, indigestion, or cause constipation.

Examples of cancers where adenocarcinomas are a common form:

- esophageal cancer; most cases in the developed world are adenocarcinomas.

- pancreas; over 80% of pancreatic cancers are ductal adenocarcinomas.

- prostate cancer is nearly always adenocarcinoma

- cervical cancer: most is squamous cell cancer, but 10–15% of cervical cancers are adenocarcinomas

- stomach cancer

Like many malignancies, penile cancer can spread to other parts of the body. It is usually a primary malignancy, the initial place from which a cancer spreads in the body. Much less often it is a secondary malignancy, one in which the cancer has spread to the penis from elsewhere. The staging of penile cancer is determined by the extent of tumor invasion, nodal metastasis, and distant metastasis.

The T portion of the AJCC TNM staging guidelines are for the primary tumor as follows:

- TX: Primary tumor cannot be assessed.

- T0: No evidence of primary tumor.

- Tis: Carcinoma "in situ".

- Ta: Noninvasive verrucous carcinoma.

- T1a: Tumor invades subepithelial connective tissue without lymph vascular invasion and is not poorly differentiated (i.e., grade 3–4).

- T1b: Tumor invades subepithelial connective tissue with lymph vascular invasion or is poorly differentiated.

- T2: Tumor invades the corpus spongiosum or cavernosum.

- T3: Tumor invades the urethra or prostate.

- T4: Tumor invades other adjacent structures.

Anatomic Stage or Prognostic Groups of penile cancer are as follows:

- Stage 0—Carcinoma "in situ".

- Stage I—The cancer is moderately or well differentiated and only affects the subepithelial connective tissue.

- Stage II—The cancer is poorly differentiated, affects lymphatics, or invades the corpora or urethra.

- Stage IIIa—There is deep invasion into the penis and metastasis in one lymph node.

- Stage IIIb—There is deep invasion into the penis and metastasis into multiple inguinal lymph nodes.

- Stage IV—The cancer has invaded into structures adjacent to the penis, metastasized to pelvic nodes, or distant metastasis is present.

Myelolipoma ("myelo-", from the ancient greek "μυελός", marrow; "lipo", meaning "of, or pertaining to, fat; "-oma", meaning tumor or mass") is a benign tumor-like lesion composed of mature adipose (fat) tissue and haematopoietic (blood-forming) elements in various proportions.

Myelolipomas can present in the adrenal gland, or outside of the gland.

The majority of myelolipomas are asymptomatic. Most do not produce any adrenal hormones. Most are only discovered as a result of investigation for another problem.

When myelolipomas do produce symptoms, it is usually because they have become large, and are pressing on other organs or tissues nearby. Symptoms include pain in the abdomen or , blood in the urine, a palpable lump or high blood pressure.

As they are benign tumors, myelolipomas do not spread to other body parts. Larger myelolipomas are at risk of localised tissue death and bleeding, which may cause a retroperitoneal haemorrhage.

In urologic pathology, high-grade prostatic intraepithelial neoplasia, abbreviated HGPIN, is an abnormality of prostatic glands and believed to precede the development of prostate adenocarcinoma (the most common form of prostate cancer).

It may be referred to simply as prostatic intraepithelial neoplasia (abbreviated as PIN). It is considered to be a pre-malignancy, or carcinoma in situ, of the prostatic glands.

Headaches as a result of raised intracranial pressure can be an early symptom of brain cancer. However, isolated headache without other symptoms is rarer, and other symptoms often occur before headaches become common. Certain warning signs for headache exist which make it more likely to be associated with brain cancer. These are as defined by the American Academy of Neurology: "abnormal neurological examination, headache worsened by Valsalva maneuver, headache causing awakening from sleep, new headache in the older population, progressively worsening headache, atypical headache features, or patients who do not fulfill the strict definition of migraine".