Most paragangliomas are either asymptomatic or present as a painless mass. While all contain neurosecretory granules, only in 1–3% of cases is secretion of hormones such as catecholamines abundant enough to be clinically significant; in that case manifestations often resemble those of pheochromocytomas (intra-medullary paraganglioma).

About 85% of paragangliomas develop in the abdomen; only 12% develop in the chest and 3% in the head and neck region (the latter are the most likely to be symptomatic). While most are single, rare multiple cases occur (usually in a hereditary syndrome). Paragangliomas are described by their site of origin and are often given special names:

- Carotid paraganglioma (carotid body tumor): Is the most common of the head and neck paragangliomas. It usually presents as a painless neck mass, but larger tumors may cause cranial nerve palsies, usually of the vagus nerve and hypoglossal nerve.

- Organ of Zuckerkandl: A collection of paraganglia near the bifurcation of the aorta, comprising a small mass of neural crest-derived chromaffin cells. Serves as a common origin of abdominal paragangliomas.

- Glomus tympanicum and Glomus jugulare: Both commonly present as a middle ear mass resulting in tinnitus (in 80%) and hearing loss (in 60%). The cranial nerves of the jugular foramen may be compressed, resulting swallowing difficulty, or ipsilateral weakness of the upper trapezius and sternocleiodomastoid muscles (from compression of the spinal accessory nerve). These patients present with a reddish bulge behind an intact ear drum. This condition is also known as the "Red drum". On application of pressure to the external ear canal with the help of a pneumatic ear speculum the mass could be seen to blanch. This sign is known as "Brown's sign". A deficient bony plate along the tympanic portion of the internal carotid artery (aberrant ICA) is a normal variant and can be mistaken with glomus jugulare.

- Vagal paraganglioma: These are the least common of the head and neck paragangliomas. They usually present as a painless neck mass, but may result in dysphagia and hoarseness.

- Pulmonary paraganglioma: These occur in the lung and may be either single or multiple.

- Other sites: Rare sites of involvement are the larynx, nasal cavity, paranasal sinuses, thyroid gland, and the thoracic inlet, as well as the bladder in extremely rare cases.

A primary tumor is a tumor growing at the anatomical site where tumor progression began and proceeded to yield a cancerous mass. Most cancers develop at their primary site but then go on to metastasize or spread to other parts of the body. These further tumors are secondary tumors.

Most cancers continue to be called after their primary site, as in breast cancer or lung cancer for example, even after they have spread to other parts of the body. Cancer of unknown primary origin is where secondary tumors are found, but the original primary site cannot be decided.

Symptoms of cancer in dogs may include:

- Lumps (which are not always malignant, but should always be examined by a vet)

- Swelling

- Persistent sores

- Abnormal discharge from any part of the body

- Bad breath

- Listlessness/lethargy

- Rapid, often unexplained weight loss

- Sudden lameness

- Offensive odor

- Black, tarry stools (a symptom of ulcers, which can be caused by mast cell tumors)

- Decreased or loss of appetite

- Difficulty breathing, urinating or defecating

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'.

Initially, nearby lymph nodes are struck early. The lungs, liver, brain, and bones are the most common metastasis locations from solid tumors.

- In lymph nodes, a common symptom is lymphadenopathy

- Lungs: cough, hemoptysis and dyspnea (shortness of breath)

- Liver: hepatomegaly (enlarged liver), nausea and jaundice

- Bones: bone pain, fracture of affected bones

- Brain: neurological symptoms such as headaches, seizures, and vertigo

Although advanced cancer may cause pain, it is often not the first symptom.

Some patients, however, do not show any symptoms.

When the organ gets a metastatic disease it begins to shrink until its lymph nodes burst, or undergo lysis.

Childhood rhabdomyosarcoma is difficult to diagnose. Factors that increase the likelihood of this cancer include Li-Fraumeni syndrome, type one Neurofibromatosis, Beckwith-Wiedemann syndrome, Costello syndrome, and Noonan syndrome. Each contribute to deformations of bones, tissue, and muscles.

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.

Childhood rhabdomyosarcoma consists of three subgroups. Embryonal is the most common among children and young adults. Alveolar and anaplastic rhabdomyosarcoma occur in the teenage years.

- Embryonal rhabdomyosarcoma develops within the first seven weeks of the embryo's development. Rapid cell growth causes masses to form along the head, neck, urinary tract, and genital organs.

- Alveolar, the second most common group, is seen later in life. During the teen years, large muscle groups come under attack, including the torso and large appendages. Aggressive treatment is needed to stop or limit progression of alveolar rhabdomyosarcoma.

- Anaplastic rhabdomyosarcoma is rarely seen in children and only precise intensive lab work can identify it.

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.

Hepatoid tumor or hepatoid [adeno]carcinoma are terms for a number of uncommon or rare neoplasms in humans, named for a visual resemblance of the cells under the microscope to those of hepatocellular carcinoma, the most common form of liver cancer. They can arise in several parts of the body, and thus form sub-types of diseases such as stomach cancer and pancreatic cancer. The WHO defines "Hepatoid carcinoma" as "An adenocarcinoma with morphologic characteristics similar to hepatocellular carcinoma , arising from an anatomic site other than the liver".

In dogs it may refer to a Perianal gland tumor, based on a similar resemblance to healthy liver cells.

Anterior urethral cancer is a disease in which malignant cancer cells are found in the part of the urethra that is closest to the outside of the body.

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.

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.

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

In medicine, the Sister Mary Joseph nodule or more commonly node, also called Sister Mary Joseph sign, refers to a palpable nodule bulging into the umbilicus as a result of metastasis of a malignant cancer in the pelvis or abdomen.

Gastrointestinal malignancies account for about half of underlying sources (most commonly gastric cancer, colonic cancer or pancreatic cancer, mostly of the tail and body of the pancreas), and men are even more likely to have an underlying cancer of the gastrointestinal tract. Gynecological cancers account for about 1 in 4 cases (primarily ovarian cancer and also uterine cancer). Nodules will also, rarely, originate from appendix cancer spillage Pseudomyxoma peritonei. Unknown primary tumors and rarely, urinary or respiratory tract malignancies cause umbilical metastases. How exactly the metastases reach the umbilicus remains largely unknown. Proposed mechanisms for the spread of cancer cells to the umbilicus include direct transperitoneal spread, via the lymphatics which run alongside the obliterated umbilical vein, hematogenous spread, or via remnant structures such as the falciform ligament, median umbilical ligament, or a remnant of the vitelline duct. Sister Mary Joseph nodule is associated with multiple peritoneal metastases and a poor prognosis.

Ninety percent of cases of head and neck cancer (cancer of the mouth, nasal cavity, nasopharynx, throat and associated structures) are due to squamous cell carcinoma.

Primary squamous cell thyroid carcinoma shows an aggressive biological phenotype resulting in poor prognosis for patients.

Neuroendocrine carcinoma affects many different parts of the body.

In the cervix, it is a rare, but very aggressive form of cervical cancer. In its early stages, neuroendocrine carcinoma is asymptomatic (not showing or producing indications of a disease or other medical condition). In more advanced stages, symptoms of Neuroendocrine carcinoma of the cervix are: abnormal vaginal bleeding, increased vaginal discharge, and pelvic pain, painful urination, pain during sex, tiredness, leg swelling, and backache. When left untreated, metastasis or even death may occur.

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)

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.

A soft-tissue sarcoma is a form of sarcoma that develops in connective tissue, though the term is sometimes applied to elements of the soft tissue that are not currently considered connective tissue.

Florid cutaneous papillomatosis (also known as the Schwartz-Burgess syndrome) is an obligate paraneoplastic syndrome.

FCP begins as the sudden onset of numerous cutaneous papillomas that are clinically indistinguishable from viral warts. The papillomas range from 1 to 3 mm in diameter may spread to involve the entire body, including the face. Pruritus, which may sometimes precede the onset of FCP, is evident in the affected regions in about half of patients. Evaluation of a skin biopsy clearly distinguishes FCP from viral warts.

FCP is associated with underlying cancer of the breast, bladder, ovary, uterus, prostate, and lung. Other associated underlying malignancies include squamous cell carcinomas and lymphomas such as non-Hodgkin's lymphoma.

FCP is sometimes seen together with other signs of internal cancer, especially malignant acanthosis nigricans, tripe palms, Leser–Trélat sign, and hypertrichosis lanuginosa acquisita. FCP tends to improve in association with surgical or chemotherapeutic therapy of the underlying internal cancer. A recurrence or exacerbation of FCP may be linked with tumor regrowth or metastatic spread.

Lymphoma is the most common form of cancer in cats, which is often associated with feline leukemia virus, and accounts for 25 percent of all cases. Feline lymphoma usually strikes the digestive system, causing excessive vomiting and diarrhea. Other common symptoms of lymphoma in cats include swollen lymph nodes, loss of appetite, weight loss, and difficulty breathing.

Mammary gland tumors are the third common type of cancer in older female cats, with the most common symptom manifesting as a in the breast tissue. The tumor is typically firm and nodular, and adheres to the overlying skin. Nipples may also appear to be red and swollen, oozing yellowish fluid.