Liposarcoma overview

# Overview
Liposarcoma is a uncommon cancer of connective tissues. Liposarcoma is a malignant tumor that arises in fat cells in deep soft tissue, such as that inside the thigh or in the retroperitoneum.
They are typically large bulky tumors which tend to have multiple smaller satellites extending beyond the main confines of the tumor.

# Historical Perspective
Liposarcoma was first described by Dr. Rudolph Virchow, a German pathologist, in 1857. Virchow reported a "myxoma lipomatoides malignum", highlighting the malignant nature of the tumor. Between 1954 and 1979, several authors reported cases of liposarcoma and suggested that liposarcoma should be classified according to histopathological analysis into well-differentiated, myxoid, and dedifferentiated subtypes.

# Classification
Liposarcoma may be classified into well-differentiated, de-differentiated, myxoid, round cell, or pleomorphic liposarcoma.

# Pathophysiology
The pathogenesis of liposarcoma depends on the histological subtype. The role of proto-oncogenes has been implicated in the development of well-differentiated liposarcoma

# Causes
There are no established causes for liposarcoma.

# Differential Diagnosis
Liposarcoma must be differentiated from other diseases that cause a painless, growing mass such as spindle cell lipoma, neurofibroma, dermatofibrosarcoma protuberans, and malignant peripheral nerve sheath tumor.

# Epidemiology and Demographics
Liposarcoma is the second most common type of all soft tissue sarcomas in adults. The annual incidence is 0.25 cases per 100,000 individuals. Men are slightly more affected with liposarcoma than women. It is most frequent in middle-aged and older adults.

# Risk Factors
Common risk factors in the development of liposarcoma include chemical carcinogens, radiation, immunodeficiency, genetic disorders, and viral infections.

# Natural History, Complications and Prognosis
Common complication of liposarcoma include metastasis.  Mass may compress adjacent structures causing different clinical manifestations. Metastasis is the most important aspect to assess in the prognosis of liposarcoma. The prognosis will depend on the histopathological subtype, being the well differentiated liposarcoma the subtype with the best prognosis, and the pleomorphic liposarcoma with the worst prognosis.

# Diagnosis

## Staging
The staging of liposarcoma is based on the TNM classification, which includes primary tumor spread, lymph node involvement, and presence of metastasis.

## History and Symptoms
Liposarcoma usually presents as a  painless mass. The most common location of a liposarcoma is the lower extremities.  Patients with retroperitoneal liposarcoma remain asymptomatic until the mass invades adjacent structures, which may cause pain or obstructive symptoms.

## Physical Examination
Physical examination findings of liposarcoma depend on the location of the tumor.  Since most liposarcomas are located in the lower extremities, liposarcoma is commonly associated with the findings of palpable firm nontender mass in one lower extremity.   Physical examination of retroperitoneal liposarcomas is usually unremarkable, but other pertinent findings on physical examination of retroperitoneal liposarcomas include palpation of an abdominal mass, abdominal distension, and tenderness.

## Laboratory Findings
There are no specific laboratory tests for the diagnosis of liposarcoma. The pertinent laboratory findings of liposarcoma include anemia and elevated BUN due to GI bleeding and elevated creatinine among patients with obstructive nephropathy.

## Biopsy
The definitive diagnosis of liposarcoma is made by biopsy, which also provides histopathological classification of the liposarcoma's subtype.

## CT
CT imaging is crucial for the diagnosis of liposarcoma. CT scan may detect regions of lipid and non-lipid components that correlate with histological subtypes of liposarcoma. CT imaging may demonstrate the size, location, and depth of a liposarcoma, as well as lymph node involvement and distant metastasis. CT findings may be correlated with the histopathological subtype.

## MRI
MRI is the optimal imaging test for the diagnosis of liposarcoma.  MRI findings for a well-differentiated liposarcoma include a mass with at least 75% of adipose content with thin irregular septa.  MRI also evaluates the size, location, and depth of the mass.  MRI findings help to differentiate between the different subtypes of liposarcoma and help to assess distant metastasis.

## Other Imaging Findings
Positron emission tomography (PET) scan is useful in cases where the liposarcoma is firm, deep, and has a size greater than 3 cm.  PET scan may also help evaluate the grade and prognosis of the tumor,as well as its shrinkage following chemotherapy.

## Other Diagnostic Studies
Li-Fraumeni syndrome is associated with liposarcoma. Mutations in the TP53 gene that encodes the tumor suppressor gene p53 cause Li-Fraumeni syndrome.

# Treatment

## Medical Therapy
Medical therapy for liposarcoma includes  Chemotherapy, chemoradiation, immunotherapy and targeted therapy.

## Surgery
The predominant therapy for liposarcoma is surgical resection. Adjunctive chemotherapy and radiation may be required.