Clinical signs are often vague and include weight loss, loss of appetite, fatigue, and possible jaundice.

Tumors that develop within the liver may be either benign (noncancerous) or malignant (cancerous). Tumors can start in the liver, or spread to the liver from another cancer in the body. Malignant liver tumors have been reported to metastasize to other organs such as regional lymph nodes, lungs, kidneys, pancreas, spleen and others.

A liver metastasis is a malignant tumor in the liver that has spread from another organ affected by cancer. The liver is a common site for metastatic disease because of its rich, dual blood supply (the liver receives blood via the hepatic artery and portal vein). Metastatic tumors in the liver are 20 times more common than primary tumors. In 50% of all cases the primary tumor is of the gastrointestinal tract, other common sites include the breast, ovaries, bronchus and kidney.

Tumor emboli entering the sinusoids through the liver blood supply appear to be physically obstructed by the Kupffer cells, but if tumor emboli are larger, they tend to become lodged in the portal venous branches.

Because liver cancer is an umbrella term for many types of cancer, the signs and symptoms depend on what type of cancer is present. Cholangiocarcinoma is associated with sweating, jaundice, abdominal pain, weight loss and liver enlargement. Hepatocellular carcinoma is associated with abdominal mass, abdominal pain, emesis, anemia, back pain, jaundice, itching, weight loss and fever.

The most frequent liver cancer, accounting for approximately 75% of all primary liver cancers, is hepatocellular carcinoma (HCC) (also named "hepatoma", which is a misnomer because adenomas are usually benign). HCC is a cancer formed by liver cells, known as hepatocytes, that become malignant. Another type of cancer formed by liver cells is hepatoblastoma, which is specifically formed by immature liver cells. It is a rare malignant tumor that primarily develops in children, and accounts for approximately 1% of all cancers in children and 79% of all primary liver cancers under the age of 15. Most hepatoblastomas form in the right lobe.

Liver cancer can also form from other structures within the liver such as the bile duct, blood vessels and immune cells. Cancer of the bile duct (cholangiocarcinoma and cholangiocellular cystadenocarcinoma) account for approximately 6% of primary liver cancers. There is also a variant type of HCC that consists of both HCC and cholangiocarcinoma. Tumors of the blood vessels (angiosarcoma and hemangioendothelioma, embryonal sarcoma and fibrosarcoma are produced from a type of connective tissue known as mesenchyme. Cancers produced from muscle in the liver are leiomyosarcoma and rhabdomyosarcoma. Other less common liver cancers include carcinosarcomas, teratomas, yolk sac tumours, carcinoid tumours and lymphomas. Lymphomas usually have diffuse infiltration to liver, but It may also form a liver mass in rare occasions.

Many cancers found in the liver are not true liver cancers, but are cancers from other sites in the body that have spread to the liver (known as metastases). Frequently, the site of origin is the gastrointestinal tract, since the liver is close to many of these metabolically active, blood-rich organs near to blood vessels and lymph nodes (such as pancreatic cancer, stomach cancer, colon cancer and carcinoid tumors mainly of the appendix), but also from breast cancer, ovarian cancer, lung cancer, renal cancer, prostate cancer.

The World Health Organization (WHO) classification scheme places neuroendocrine tumors into three main categories, which emphasize the tumor grade rather than the anatomical origin:

- well-differentiated neuroendocrine tumours, further subdivided into tumors with benign and those with uncertain behavior

- well-differentiated (low grade) neuroendocrine carcinomas with low-grade malignant behavior

- poorly differentiated (high grade) neuroendocrine carcinomas, which are the large cell neuroendocrine and small cell carcinomas.

Additionally, the WHO scheme recognizes mixed tumors with both neuroendocrine and epithelial carcinoma features, such as goblet cell cancer, a rare gastrointestinal tract tumor.

Placing a given tumor into one of categories depends on well-defined histological features: size, lymphovascular invasion, mitotic counts, Ki-67 labelling index, invasion of adjacent organs, presence of metastases and whether they produce hormones.

Carcinoids most commonly affect the small bowel, particularly the ileum, and are the most common malignancy of the appendix. Many carcinoids are asymptomatic and are discovered only upon surgery for unrelated causes. These coincidental carcinoids are common; one study found that one person in ten has them. Many tumors do not cause symptoms even when they have metastasized. Other tumors even if very small can produce adverse effects by secreting hormones.

Ten per cent (10%) or less of carcinoids, primarily some midgut carcinoids, secrete excessive levels of a range of hormones, most notably serotonin (5-HT) or substance P, causing a constellation of symptoms called carcinoid syndrome:

- flushing

- diarrhea

- asthma or wheezing

- congestive heart failure (CHF)

- abdominal cramping

- peripheral edema

- heart palpitations

A carcinoid crisis with profound flushing, bronchospasm, tachycardia, and widely and rapidly fluctuating blood pressure can occur if large amounts of hormone are acutely secreted, which is occasionally triggered by factors such as diet, alcohol, surgery chemotherapy, embolization therapy or radiofrequency ablation.

Chronic exposure to high levels of serotonin causes thickening of the heart valves, particularly the tricuspid and the pulmonic valves, and over a long period can lead to congestive heart failure. However, valve replacement is rarely needed. The excessive outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency, and thus pellagra, which is associated with dermatitis, dementia, and diarrhea. Many other hormones can be secreted by some of these tumors, most commonly growth hormone that can cause acromegaly, or cortisol, that can cause Cushing's syndrome.

Occasionally, haemorrhage or the effects of tumor bulk are the presenting symptoms. Bowel obstruction can occur, sometimes due to fibrosing effects of NET secretory products with an intense desmoplastic reaction at the tumor site, or of the mesentery.

Krukenberg tumors often come to the attention when they cause abdominal or pelvic pain, bloating, ascites, or pain during sexual intercourse. Krukenberg tumors can occasionally provoke a reaction of the ovarian stroma which leads to hormone production, that results in vaginal bleeding, a change in menstrual habits, or hirsutism, or occasionally virilization as a main symptom.

All these symptoms are non-specific and can also arise with a range of problems other than cancer, and a diagnosis can only be made following confirmatory investigations such as computed tomography (CT) scans, laparotomy and/or a biopsy of the ovary.

Cholangiocarcinoma, also known as bile duct cancer, is a form of cancer that is composed of mutated epithelial cells (or cells showing characteristics of epithelial differentiation) that originate in the bile ducts which drain bile from the liver into the small intestine. Other biliary tract cancers include gallbladder cancer and cancer of the ampulla of Vater.

Cholangiocarcinoma is a relatively rare neoplasm that is classified as an adenocarcinoma (a cancer that forms glands or secretes significant amounts of mucins). It has an annual incidence rate of 1–2 cases per 100,000 in the Western world, but rates of cholangiocarcinoma have been rising worldwide over the past few decades.

Prominent signs and symptoms of cholangiocarcinoma include abnormal liver function tests, abdominal pain, jaundice, and weight loss. Other symptoms such as generalized itching, fever, and changes in color of stool or urine may also occur. The disease is diagnosed through a combination of blood tests, imaging, endoscopy, and sometimes surgical exploration, with confirmation obtained after a pathologist examines cells from the tumor under a microscope. Known risk factors for cholangiocarcinoma include primary sclerosing cholangitis (an inflammatory disease of the bile ducts), infection with the parasitic liver flukes "Opisthorchis viverrini" or "Clonorchis sinensis", some congenital liver malformations, and exposure to Thorotrast (thorium dioxide), a chemical formerly used in medical imaging. However, most people with cholangiocarcinoma have no identifiable risk factors.

Cholangiocarcinoma is considered to be an incurable and rapidly lethal cancer unless both the primary tumor and any metastases can be fully removed by surgery. No potentially curative treatment exists except surgery, but most people have advanced stage disease at presentation and are inoperable at the time of diagnosis. People with cholangiocarcinoma are generally managed - though not cured - with chemotherapy, radiation therapy, and other palliative care measures. These are also used as additional therapies after surgery in cases where resection has apparently been successful (or nearly so).

Since pancreatic cancer usually does not cause recognizable symptoms in its early stages, the disease is typically not diagnosed until it has spread beyond the pancreas itself. This is one of the main reasons for the generally poor survival rates. Exceptions to this are the functioning PanNETs, where over-production of various active hormones can give rise to symptoms (which depend on the type of hormone).

Bearing in mind that the disease is rarely diagnosed before the age of 40, common symptoms of pancreatic adenocarcinoma occurring before diagnosis include:

- Pain in the upper abdomen or back, often spreading from around the stomach to the back. The location of the pain can indicate the part of the pancreas where a tumor is located. The pain may be worse at night and may increase over time to become severe and unremitting. It may be slightly relieved by bending forward. In the UK, about half of new cases of pancreatic cancer are diagnosed following a visit to a hospital emergency department for pain or jaundice. In up to two-thirds of people abdominal pain is the main symptom, for 46% of the total accompanied by jaundice, with 13% having jaundice without pain.

- Jaundice, a yellow tint to the whites of the eyes or skin, with or without pain, and possibly in combination with darkened urine. This results when a cancer in the head of the pancreas obstructs the common bile duct as it runs through the pancreas.

- Unexplained weight loss, either from loss of appetite, or loss of exocrine function resulting in poor digestion.

- The tumor may compress neighboring organs, disrupting digestive processes and making it difficult for the stomach to empty, which may cause nausea and a feeling of fullness. The undigested fat leads to foul-smelling, fatty feces that are difficult to flush away. Constipation is common.

- At least 50% of people with pancreatic adenocarcinoma have diabetes at the time of diagnosis. While long-standing diabetes is a known risk factor for pancreatic cancer (see Risk factors), the cancer can itself cause diabetes, in which case recent onset of diabetes could be considered an early sign of the disease. People over 50 who develop diabetes have eight times the usual risk of developing pancreatic adenocarcinoma within three years, after which the relative risk declines.

Other common manifestations of the disease include: weakness and tiring easily; dry mouth; sleep problems; and a palpable abdominal mass."

While most carcinoids are asymptomatic through the natural lifetime and are discovered only upon surgery for unrelated reasons (so-called "coincidental carcinoids"), all carcinoids are considered to have malignant potential.

About 10% of carcinoids secrete excessive levels of a range of hormones, most notably serotonin (5-HT), causing:

- Flushing (serotonin itself does not cause flushing). Potential causes of flushing in carcinoid syndrome include bradykinins, prostaglandins, tachykinins, substance P, and/or histamine, diarrhea, and heart problems. Because of serotonin's growth-promoting effect on cardiac myocytes,[14] a serotonin-secreting carcinoid tumour may cause a tricuspid valve disease syndrome, due to the proliferation of myocytes onto the valve.

- Diarrhea

- Wheezing

- Abdominal cramping

- Peripheral edema

The outflow of serotonin can cause a depletion of tryptophan leading to niacin deficiency. Niacin deficiency, also known as pellagra, is associated with dermatitis, dementia, and diarrhea.

This constellation of symptoms is called "carcinoid syndrome" or (if acute) "carcinoid crisis". Occasionally, haemorrhage or the effects of tumor bulk are the presenting symptoms. The most common originating sites of carcinoid is the small bowel, particularly the ileum; carcinoid tumors are the most common malignancy of the appendix. Carcinoid tumors may rarely arise from the ovary or thymus.

They are most commonly found in the midgut at the level of the ileum or in the appendix. The next most common affected area is the respiratory tract, with 28% of all cases — per PAN-SEER data (1973 – 1999). The rectum is also a common site.

A Krukenberg tumor refers to a malignancy in the ovary that metastasized from a primary site, classically the gastrointestinal tract, although it can arise in other tissues such as the breast. Gastric adenocarcinoma, especially at the pylorus, is the most common source. Krukenberg tumors are often (over 80%) found in both ovaries, consistent with its metastatic nature.

Carcinoid (also carcinoid tumor) is a slow-growing type of neuroendocrine tumor originating in the cells of the neuroendocrine system. In some cases, metastasis may occur. Carcinoid tumors of the midgut (jejunum, ileum, appendix, and cecum) are associated with carcinoid syndrome.

Carcinoid tumors are the most common malignant tumor of the appendix, but they are most commonly associated with the small intestine, and they can also be found in the rectum and stomach. They are known to grow in the liver, but this finding is usually a manifestation of metastatic disease from a primary carcinoid occurring elsewhere in the body. They have a very slow growth rate compared to most malignant tumors. The median age at diagnosis for all patients with neuroendocrine tumors is 63 years.

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.

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.

Macroscopically, liver cancer appears as a nodular or infiltrative tumor. The nodular type may be solitary (large mass) or multiple (when developed as a complication of cirrhosis). Tumor nodules are round to oval, gray or green (if the tumor produces bile), well circumscribed but not encapsulated. The diffuse type is poorly circumscribed and infiltrates the portal veins, or the hepatic veins (rarely).

Microscopically, there are four architectural and cytological types (patterns) of hepatocellular carcinoma: fibrolamellar, pseudoglandular (adenoid), pleomorphic (giant cell) and clear cell. In well-differentiated forms, tumor cells resemble hepatocytes, form trabeculae, cords, and nests, and may contain bile pigment in the cytoplasm. In poorly differentiated forms, malignant epithelial cells are discohesive, pleomorphic, anaplastic, giant. The tumor has a scant stroma and central necrosis because of the poor vascularization.

The prognosis of HCC is affected by the staging of the tumor as well as the liver's function due to the effects of liver cirrhosis.

There are a number of staging classifications for HCC available; however, due to the unique nature of the carcinoma in order to fully encompass all the features that affect the categorization of the HCC, a classification system should incorporate; tumor size and number, presence of vascular invasion and extrahepatic spread, liver function (levels of serum bilirubin and albumin, presence of ascites and portal hypertension) and general health status of the patient (defined by the ECOG classification and the presence of symptoms).

Out of all the staging classification systems available the Barcelona Clinic Liver Cancer (BCLC) staging classification encompasses all of the above characteristics. This staging classification can be used in order to select people for treatment.

Important features that guide treatment include the following:

- size

- spread (stage)

- involvement of liver vessels

- presence of a tumor capsule

- presence of extrahepatic metastases

- presence of daughter nodules

- vascularity of the tumor

MRI is the best imaging method to detect the presence of a tumor capsule.

The most common sites of metastasis are the lung, abdominal lymph nodes, and bone.

Treatment can consist of surgery (hepatectomy), chemotherapy and/or therapies specifically aimed at the liver like radiofrequency ablation, transcatheter arterial chemoembolization, selective internal radiation therapy and irreversible electroporation. For most patients no effective treatment exists because both lobes are usually involved, making surgical resection impossible. Younger patients with metastases from colorectal cancer confined to one lobe of the liver and up to 4 in number may be treated by partial hepatectomy. In selected cases, chemotherapy may be given systemically or via hepatic artery.

In some tumors, notably those arising from the colon and rectum, apparently solitary metastases

or metastases to one or other lobes may be resected. A careful search for other metastases is required, including local recurrence of the original primary tumor (e.g., via colonoscopy) and dissemination elsewhere (e.g., via CT of the thorax). 5 year survival rates of 30-40% have been reported following resection.

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'.

The most common physical indications of cholangiocarcinoma are abnormal liver function tests, jaundice (yellowing of the eyes and skin occurring when bile ducts are blocked by tumor), abdominal pain (30%–50%), generalized itching (66%), weight loss (30%–50%), fever (up to 20%), and changes in the color of stool or urine. To some extent, the symptoms depend upon the location of the tumor: patients with cholangiocarcinoma in the extrahepatic bile ducts (outside the liver) are more likely to have jaundice, while those with tumors of the bile ducts within the liver more often have pain without jaundice.

Blood tests of liver function in patients with cholangiocarcinoma often reveal a so-called "obstructive picture," with elevated bilirubin, alkaline phosphatase, and gamma glutamyl transferase levels, and relatively normal transaminase levels. Such laboratory findings suggest obstruction of the bile ducts, rather than inflammation or infection of the liver parenchyma, as the primary cause of the jaundice.

Papillary thyroid carcinoma is usually discovered on routine examination as an asymptomatic thyroid nodule that appears as a neck mass. In some instances, the mass may have produced local symptoms. This mass is normally referred to a fine needle aspiration biopsy (FNA) for investigation. FNA accuracy is very high and it is a process widely used in these cases. Other investigation methods include ultrasound imaging and nuclear scan. The ultrasound is a useful test to distinguish solid from cystic lesions and to identify calcifications. The thyroid ultrasound is also very effective to discover microcarcinomas, which refer to very small carcinomas (<1 cm).

Papillary thyroid carcinomas are also discovered when a hard nodule is found in multinodular goiter, when enlarged cervical lymph nodes are detected, or when there are unidentified metastatic lesions elsewhere in the body. Expanding lesions found in the thyroid gland, especially if they are painful, should be examined as they may indicate the presence of papillary thyroid carcinoma. Other clinical signs that could indicate papillary thyroid are fixation to the trachea, a firm neck mass, damage to recurrent laryngeal or cervical sympathetic nerves. Five percent of the population can have thyroid nodules, and the majority will be benign.

Appropriate workup includes an ultrasound of the neck, followed by lab studies. Patients will usually meet with both an endocrinologist and a surgeon (head and neck surgeon or endocrine surgeon).

Papillary thyroid cancer or papillary thyroid carcinoma is the most common type of thyroid cancer, representing 75 percent to 85 percent of all thyroid cancer cases. It occurs more frequently in women and presents in the 20–55 year age group. It is also the predominant cancer type in children with thyroid cancer, and in patients with thyroid cancer who have had previous radiation to the head and neck. It is often well-differentiated, slow-growing, and localized, although it can metastasize.

In addition to renal cell carcinoma and renal pelvis carcinoma, other, less common types of kidney cancer include:

- Squamous cell carcinoma

- Juxtaglomerular cell tumor (reninoma)

- Angiomyolipoma

- Bellini duct carcinoma

- Clear-cell sarcoma of the kidney

- Mesoblastic nephroma

- Wilms' tumor, usually is reported in children under the age of 5.

- Mixed epithelial stromal tumor

Rarely, some other types of cancer and potentially cancerous tumors that more usually originate elsewhere can originate in the kidneys. These include:

- Clear cell adenocarcinoma

- Transitional cell carcinoma

- Inverted papilloma

- Renal lymphoma

- Teratoma

- Carcinosarcoma

- Carcinoid tumor of the renal pelvis

Cancer in the kidney may also be secondary, the result of metastasis from a primary cancer elsewhere in the body.

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.