Kaposi's sarcoma overview

# Overview
Kaposi's sarcoma arises from endothelial cells, which are epithelial cells that normally lines the luminal surface of blood vessels and lymphatic vessels. Kaposi's sarcoma is mainly caused by an infection with Human herpes virus 8 (HHV-8), which is also known as Kaposi's sarcoma-associated herpes virus (KSHV). The main gene involved in the pathogenesis of Kaposi's sarcoma is ORF73 gene, which encodes the viral latency-associated nuclear antigen (LANA-1). Kaposi's sarcoma is commonly associated with acquired immune deficiency syndrome (AIDS). On gross pathology, reddish, violaceous, or bluish-black macules and patches are characteristic findings of Kaposi's sarcoma. On microscopic histopathological analysis the presence of spindle cells with minimal nuclear atypia are characteristic findings of Kaposi's sarcoma. Kaposi's sarcoma may be classified according to the clinical setting of the disease into five subtypes: Classic Kaposi's sarcoma, African cutaneous Kaposi's sarcoma, African lymphadenopathic Kaposi's sarcoma, Iatrogenic Kaposi's sarcoma, and AIDS-associated Kaposi's sarcoma. The epidemiology of Kaposi sarcoma varies depending on its specific subtype. Before the AIDS epidemic, Kaposi's sarcoma was relatively rare. In the early epidemic of AIDS, the incidence of HIV-related Kaposi sarcoma significantly increased; however, antiretroviral therapy led to a decrease in the incidence of HIV-related Kaposi sarcoma. While endemic African Kaposi sarcoma is more common in African Bantu, classic Kaposi sarcoma is more prevalent in Middle Eastern countries particularly among males and individuals from Jewish descent.  The incidence of Kaposi sarcoma is markedly increased in renal transplant patients ranging from 0.5% to 5.3%.  Transplant-related Kaposi sarcoma occurs more commonly in individuals who have Jewish, Arabic, Mediterranean, African, or Caribbean ethnicity.  In the United States, the age-adjusted prevalence of Kaposi sarcoma is 8.1 per 100,000 in 2011. The most potent risk factor in the development of Kaposi's sarcoma is an immune deficiency state. There is no established system for the staging of Kaposi's sarcoma among immune competent patients. However, the staging of AIDS-associated Kaposi's sarcoma is based on the  AIDS Clinical Trials Group (ACTG) staging system. Symptoms of Kaposi's sarcoma include fever, abdominal pain, hematochezia, hemoptysis, and gradual development of red/violaceous macules and patches over the nose, legs, and feet. The optimal therapy for Kaposi's sarcoma depends on multiple factors. Management strategies varies depending on the specific variant of Kaposi's sarcoma. Classic Kaposi's sarcoma management may range from no treatment to either radiotherapy, local therapeutic interventions, or surgical excision. Iatrogenic Kaposi's sarcoma management focuses on modifying immunosuppressive therapy in addition to local therapeutic interventions. Endemic Kaposi's sarcoma is primarily managed by systemic chemotherapy. However, there is no curative treatment for epidemic Kaposi's sarcoma; the mainstay management for such patients is HAART therapy which aims for the control of Kaposi's sarcoma progression. Local/regional therapy recommended for the management of Kaposi's sarcoma patients may include surgical excision, cryotherapy, and sclerotherapy.

# Historical Perspective
Kaposi's sarcoma was first described by Dr. Moritz Kaposi, a Hungarian dermatologist at the University of Vienna, in the year 1872

# Classification
Kaposi's sarcoma may be classified according to the clinical setting of the disease into five subtypess: Classic Kaposi's sarcoma, African cutaneous Kaposi's sarcoma, African lymphadenopathic Kaposi's sarcoma, Iatrogenic Kaposi's sarcoma, and AIDS-associated Kaposi's sarcoma.

# Pathophysiology
Kaposi's sarcoma arises from endothelial cells, which are epithelial cells that normally lines the luminal surface of blood vessels and lymphatic vessels. Kaposi's sarcoma is mainly caused by an infection with Human herpes virus 8 (HHV-8), which is also known as Kaposi's sarcoma-associated herpes virus (KSHV). The main gene involved in the pathogenesis of Kaposi's sarcoma is ORF73 gene, which encodes the viral latency-associated nuclear antigen (LANA-1). Kaposi's sarcoma is commonly associated with acquired immune deficiency syndrome (AIDS). On gross pathology, reddish, violaceous, or bluish-black macules and patches are characteristic findings of Kaposi's sarcoma. On microscopic histopathological analysis the presence of spindle cells with minimal nuclear atypia are characteristic findings of Kaposi's sarcoma

# Causes
Kaposi's sarcoma is caused by an infection with HHV-8. The term Kaposi's sarcoma associated virus(KHSV) was coined in order to name the viral causes.

# Differentiating Kaposi's sarcoma from other Diseases
Kaposi's sarcoma must be differentiated from other diseases that cause similar cutaneous, pulmonary, and gastrointestinal involvement, such as bacillary angiomatosis, AIDS-related lymphoma, and seborrheic keratosis

# Epidemiology and Demographics
The epidemiology of Kaposi sarcoma varies depending on the specific subtype. Before the AIDS epidemic, Kaposi's sarcoma was relatively rare. In the early epidemic of AIDS, the incidence of HIV-related Kaposi sarcoma significantly increased; however, antiretroviral therapy led to a decrease in the incidence of HIV-related Kaposi sarcoma. While endemic African Kaposi sarcoma is more common in African Bantu, classic Kaposi sarcoma is more prevalent in Middle Eastern countries particularly among males and individuals from Jewish descent.  The incidence of Kaposi sarcoma is markedly increased in renal transplant patients ranging from 0.5% to 5.3%.  Transplant-related Kaposi sarcoma occurs more commonly in individuals who have Jewish, Arabic, Mediterranean, African, or Caribbean ethnicity.  In the United States, the age-adjusted prevalence of Kaposi sarcoma is 8.1 per 100,000 in 2011

# Risk Factors
The most potent risk factor in the development of Kaposi's sarcoma is an immune deficiency state. Other risk factors include multiple sexual partners, homosexual males, and medical procedures such as blood transfusions and organ transplantation .

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

# Natural History, Complications and Prognosis
The prognosis of Kaposi's sarcoma depends on its histological type, whether the cancer has spread, and the general health status of the patient. When stratified by age, the 5-year relative survival of patients with Kaposi sarcoma was 68.6% and 87.5% for patients <65 and  65 years of age respectively.

# Diagnosis

## Staging
There is no established system for the staging of Kaposi's sarcoma among immune competent patients. However, the staging of AIDS-associated Kaposi's sarcoma is based on the  AIDS Clinical Trials Group (ACTG) staging system. According to the ACTG staging system, there are 2 groups of AIDS-associated Kaposi's sarcoma based on the tumor size, patients immune status, and the presence of any systemic illness

## History and Symptoms
Symptoms of Kaposi's sarcoma include fever, abdominal pain, hematochezia, hemoptysis, and gradual development of red/violaceous macules and patches over the nose, legs, and feet

## Physical Examination
Kaposi's sarcoma lesions are nodules or patches that may be purple, red, blue, or black in color and are usually located on the nose, legs, and feet.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of Kaposi's sarcoma include decreased hemoglobin level, positive HIV tests, and positive HHV-8 antigen on immunohistochemistry.

## Chest X-Ray
Chest X-ray may be helpful in the diagnosis of Kaposi's sarcoma lesions that are located in the lungs. Findings on chest X-ray suggestive of Kaposi's sarcoma include parenchymal nodular or reticular opacities, pleural effusion, and mediastinal/hilar lymphadenopathy.

## CT Scan
CT scan may be helpful in the diagnosis of Kaposi's sarcoma lesions. Findings on CT scan of the chest suggestive of Kaposi's sarcoma include ill-defined (flame-shaped) nodular lung opacities, interlobular septal thickening, and hilar lymphadenopathy.

## Other Imaging Findings
Scintigraphy may be helpful in the diagnosis of Kaposi's sarcoma.

## Other Diagnostic Studies
Other diagnostic studies for Kaposi's sarcoma include endoscopy, bronchoscopy, and biopsy.

# Treatment

## Medical Therapy
The optimal therapy for Kaposi's sarcoma depends on multiple factors. Management strategies varies depending on the specific variant of Kaposi's sarcoma. Classic Kaposi's sarcoma management may range from no treatment to either radiotherapy, local therapeutic interventions, or surgical excision. Iatrogenic Kaposi's sarcoma management focuses on modifying immunosuppressive therapy in addition to local therapeutic interventions. Endemic Kaposi's sarcoma is primarily manage by systemic chemotherapy. However, there is no curative treatment for epidemic Kaposi's sarcoma; the mainstay management for such patients is HAART therapy which aims for the control of Kaposi's sarcoma progression.

## Surgery
Local/regional therapy recommended for the management of Kaposi's sarcoma patients may include surgical excision, cryotherapy, and sclerotherapy.