Liver mass overview

# Overview
Liver mass (also known as "hepatic mass") is generally defined as the neoplastic growth of tissue in the liver. Abnormal growths found in the liver can be benign or malignant. Liver mass may be classified according to imaging features (hyperechoic vs. hypoechoic), histopathological origin (benign vs. malignant), and distribution (single/focal/solitary vs. multiple). The most common cause of a liver mass is liver cancer. Common causes of benign liver mass, include: hepatic hemangioma, focal nodular hyperplasia, hepatic adenoma, idiopathic noncirrhotic portal hypertension (including nodular regenerative hyperplasia, regenerative nodules. Conversely, common causes of malignant liver mass, include: hepatocellular carcinoma, cholangiocarcinoma, metastatic disease.  "Primary liver tumors", which originate in the liver or from hepatic-derived cells and tissues, and "secondary tumors" which originate in other sites and metastasize to the liver. Liver masses are common. The annual incidence rate of malignant liver mass is approximately 6 per 100,000 individuals in the United States. The incidence rate of liver mass increases with age; The median age at diagnosis varies widely between 5 to 60 years. Females are more commonly affected with benign liver masses than males. The female to male ratio is approximately 2.3 to 1. However, males are more commonly affected with malignant liver masses than females. The male to female ratio is approximately  3 to 1. The incidence of malignant liver mass varies widely according to the ethnicity and geographic location. A hallmark feature in the evaluation of liver mass is the malignancy assessment. The evaluation approach of liver mass will mainly depend in the initial morphological evaluation of the mass (size, margins, contours, imaging pattern, and growth). Other characteristics, such as: location, clinical features, and distribution may be helpful for the therapeutical management, surveillance, and follow-up of liver mass. Liver mass can be divided into 2 categories: benign liver mass and malignant liver mass. Based upon these categories, complementary diagnostic studies and management, include: PET/CT scan, MRI, and surgical resection. In the majority of cases, liver masses are asymptomatic and are usually found incidentally. However, in some cases, patients may develop non-specific symptoms, such as: right upper quadrant abdominal pain, pruritus, and unintentional weight loss. A positive history of chronic hepatitis, cirrhosis, nonalcoholic fatty liver disease, prolonged contraceptive use, and alcohol abuse may be suggestive of a liver mass. Symptoms related with liver mass will vary depending on the size and location of the tumor. For instance, compression symptoms from left lobe lesions, such as early satiety.  Other symptoms of liver mass may also include: loss of appetite, fatigue, nausea, and vomiting.

# Historical Perspective
Liver mass as a separate entity was first described in detail by Hippocrates. He was also the first to differentiate liver abscess from other liver masses. In 1843, Dr. Robert Liston, a British surgeon, was the first to describe hemangioma. In 1911, Yamagiwa suggested a new classification system based on the cell of origin and divided hepatobiliary cancers into hepatocellular cancer and cholangiocellular cancer, with the proposed terminology of hepatoma and cholangioma. In 1958, I Bartok discovered hepatoblastoma for the first time.

# Classification
A liver mass may be grouped into several subtypes based on the number of nodules (solitary or multiple), type of histopathology (benign or malignant), and consistency (solid or cystic).

# Causes
The most common cause of a liver mass is hepatocellular carcinoma. Common causes of benign liver mass, include: hepatic hemangioma, focal nodular hyperplasia, hepatic adenoma, idiopathic non-cirrhotic portal hypertension, nodular regenerative hyperplasia, regenerative nodules. Common causes malignant liver masses, include: hepatocellular carcinoma, cholangiocarcinoma, metastatic disease

# Differentiating Liver Mass from Other Diseases
Liver mass may be differentiated according to clinical features, laboratory findings, imaging features, histological features, and genetic studies, from other diseases that cause abdominal pain, pruritus, low-grade fever, and ascites. Common differential diagnosis includes: liver abscess, simple liver cyst, and fungal infections.

# Epidemiology and Demographics
Liver masses are common. The annual incidence rate of malignant liver mass is approximately 6 per 100,000 individuals in the United States. The incidence rate of liver mass increases with age; The median age at diagnosis varies widely between 5 to 60 years. Females are more commonly affected with benign liver masses than males. The female to male ratio is approximately 2.3 to 1. However, males are more commonly affected with malignant liver masses than females. The male to female ratio is approximately  3 to 1. The incidence of malignant liver mass varies widely according to the ethnicity and geographic location.

# Screening
According to the the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for liver mass.

# Diagnosis

## Evaluation of Liver Mass
A hallmark feature in the evaluation of liver mass is the malignancy assessment. The evaluation approach of liver mass will mainly depend in the initial morphological evaluation of the mass (size, margins, contours, imaging pattern, and growth). Other characteristics, such as: location, clinical features, and distribution may be helpful for the therapeutical management, surveillance, and follow-up of liver mass. Liver mass can be divided into 2 categories benign liver mass and malignant liver mass. Based upon these categories, recommended complementary diagnostic studies include PET/CT scan, MRI, and surgical resection.

## Staging
According to the American Joint Committee on Cancer (AJCC) staging system, there are 4 stages of malignant liver mass, based on 3 factors: tumor size, lymph node invasion, and metastasis. Each stage is assigned a letter and a number that designate T for tumor size, N for node invasion, and M for metastasis.

## History and Symptoms
In the majority of cases, liver masses are asymptomatic and are usually found incidentally. However, in some cases, patients may develop non-specific symptoms, such as: right upper quadrant abdominal pain, pruritus, and unintentional weight loss. A positive history of chronic hepatitis, cirrhosis, nonalcoholic fatty liver disease, prolonged contraceptive use, and alcohol abuse may be suggestive of a liver mass. Symptoms related with liver mass will vary depending on the size and location of the tumor. For instance, compression symptoms from left lobe lesions, such as early satiety.  Other symptoms of liver mass may also include: loss of appetite, fatigue, nausea, and vomiting.

## Physical Examination
Physical examination findings of liver mass will depend on location and size of the tumor. Usually large liver tumors may cause pain and tenderness in palpation of the abdomen due to stretching of the liver capsule. On the other hand, liver masses with smaller size can present with no remarkable findings. Common physical examination of patients with liver mass, may include: janudice, hepatomegaly, abdominal tenderness, splenomegaly, abdominal wall vascular collaterals, and weight loss.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of liver mass include: elevated serum alpha-fetoprotein level, positive serologic testing for hepatitis B/C surface antigen, and abnormal liver function tests.Routinary laboratory findings associated with liver mass, include: complete blood count, electrolytes, calcium, alkaline phosphatase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, creatinine, albumin, and lactate dehydrogenase.

## Imaging
Ultrasound is the initial method of choice for the evaluation of liver mass. The evaluation of liver mass will depend on several characteristics, such as:  vascular pattern, margins, location, distribution, and attenuation. Further evaluation of liver mass, should include other diagnostic studies, such as: triphasic CT scan with complementary tumoral markers,or MRI. Other imaging study useful for the malignancy evaluation of liver mass is PET scanning, which may be helpful for the detection of occult disease and malignancy assessment.

## X Ray
On conventional radiography there are no characteristic findings of liver mass.

## CT
Computed tomography may be useful for the evaluation and diagnosis of liver masses. The evaluation of liver mass should be performed with a triphasic CT, this modality includes 3 phases: non-contrast, arterial phase, and portal venous phase. On CT, characteristic findings of liver mass, may include: solitary or multiple lesion, solid or cystic consistency, and normally a rounded lesion. The evaluation of liver mass will depend on several characteristics, such as: vascular pattern, size, location, size, distribution, margins, attenuation, and contrast enhancement.

## MRI
On MRI, characteristic features for the diagnosis of liver mass, include: higher soft tissue contrast, lack of radiation exposure, lesion characterization by evaluation of signal intensities, improving detection of hypervascular lesions, and characterization of the dynamics of contrast uptake.

## Other Diagnostic Studies

## Biopsy
Biopsy for liver mass may be classified into 2 categories: non-surgical biopsy and surgical biopsy. Biopsy findings associated with liver mass will depend on tumor histology. Common types of liver tissue biopsy for liver mass, include: channels lined by benign endothelium, fibromuscular hyperplasia, and loss of reticulin scaffold. Common indications for biopsy in liver mass, include: suspected hepatocellular carcinoma, and unspecific imaging findings. The most important contraindication for biopsy in liver mass is suspected liver hemangioma.

# Treatment

## Medical Therapy
The majority of cases of liver masses (benign liver tumors) are asymptomatic and require only supportive care. Medical therapy is indicated only in cases of infectious cystic lesions. Surgery is the main stay of treatment for solid lesions.

## Surgery
In the majority of cases of benign hepatic tumors, patients are asymptomatic, and no treatment is indicated. The main indication for treatment is the presence of significant clinical symptoms or suspicion of malignancy or fear of malignant transformation. Surgery is the mainstay of treatment for symptomatic benign liver lesions.

## Primary Prevention
Effective measures for the primary prevention of liver lesions include limited use of OCP's, vaccination for hepatitis, alcohol cessation, especially in cirrhotic patients, avoidance of hepatotoxic drugs, physical exercise, smoking cessation, adequate caloric intake, prevention of obesity, screening of blood donors for Hepatitis B, Hepatitis C.

## Secondary Prevention
Secondary preventive measures of liver mass are similar to primary preventive measures.