Follicular lymphoma overview

# Overview
Follicular lymphoma is defined as a lymphoma of follicle center B-cells (centrocytes and centroblasts). It is a type of non Hodgkin's lymphoma. Follicular lymphoma is caused by translocation between the chromosomes 14 and 18 that results in the overexpression of the BCL-2 gene. The progression to follicular lymphoma involves the microRNAs (miRNAs).On microscopic histopathological analysis, centrocytes and centroblasts are the characteristic findings of follicular lymphoma. Follicular lymphoma may be classified according to WHO criteria into 3 subtypes: low grade follicular lymphoma, high grade follicular lymphoma and diffuse large B cell lymphoma. The prevalence of follicular lymphoma increases with age. Women are more commonly affected with follicular lymphoma than men. The prognosis is generally poor and the 5-year survival rate is approximately 72-77%. The most common symptoms of follicular lymphoma include fever, weight loss, night sweats, skin rash, painless swelling in the neck, axilla, groin, thorax, and abdomen, and chest pain, abdominal pain, and bone pain. Common physical examination findings of follicular lymphoma include fever, rash, splenomegaly, peripheral lymphadenopathy, central lymphadenopathy, chest tenderness, abdominal tenderness, and bone tenderness. Laboratory tests for  the diagnosis of follicular lymphoma include lymph node biopsy, complete blood count (CBC), blood chemistry studies, cytogenetics studies, flow cytometry, immunohistochemistry, FISH, genetic testing, and immunophenotyping. CT, MRI, and PET may be helpful in the diagnosis and assessing the spread of follicular lymphoma. Other diagnostic studies for the diagnosis of follicular lymphoma include bone marrow aspiration and biopsy, laparoscopy, and laparotomy. The optimal therapy for follicular lymphoma depends on the stage at diagnosis, age, and prognostic scores. The predominant therapy for follicular lymphoma is chemotherapy. Adjunctive hematopoietic stem cell transplantation, and radioimmunotherapy may be required.

# Classification
Follicular lymphoma may be classified according to WHO criteria into 3 subtypes: low grade follicular lymphoma, high grade follicular lymphoma and diffuse large B cell lymphoma. Three variants of follicular lymphoma include pediatric follicular lymphoma, primary intestinal follicular lymphoma, and other extranodal follicular lymphoma.

# Pathophysiology
Genes involved in the pathogenesis of follicular lymphoma include BCL-2 and BCL-6. The most common cause is reciprocal translocation t(14;18)(q32;q21). The progression to follicular lymphoma involves microRNAs (miRNAs). On microscopic histopathological analysis, centrocytes, centroblasts along with various non-neoplastic cells including T cells, follicular dendritic cells, and macrophages are the characteristic findings of follicular lymphoma.

# Causes
Follicular lymphoma may be caused by translocation between chromosome 14 and 18 that results in the overexpression of the BCL-2 gene.

# Differential Diagnosis
Follicular lymphoma must be differentiated from other diseases  such as diffuse large B cell lymphoma, Mucosa-Associated Lymphatic Tissue lymphoma (MALT), small cell lymphocytic lymphoma, and mantle cell lymphoma (MCL).

# Epidemiology and Demographics
The prevalence of follicular lymphoma increases with age. Women are more commonly affected with follicular lymphoma than men.

# Screening
Screening for follicular lymphoma is not recommended.

# Prognosis
The Prognosis is generally poor and the 5 year survival rate is approximately 72-77%.

# Diagnosis

## Staging
According to the Lugano classification, there are four stages of follicular lymphoma based on the number of nodes and extranodal involvement.

## Symptoms
The most common symptoms of follicular lymphoma include fever, weight loss, night sweats, skin rash, painless swelling in the neck,under arm, groin, thorax, and abdomen, and chest pain, abdominal pain, and bone pain.

## Physical Examination
Common physical examination findings of follicular lymphoma include fever, rash, splenomegaly, peripheral lymphadenopathy, central lymphadenopathy, chest tenderness, abdominal tenderness, and bone tenderness.

## Laboratory Findings
Laboratory tests for the diagnosis of follicular lymphoma include complete blood count (CBC), blood chemistry studies, cytogenetics studies, flow cytometry, immunohistochemistry, FISH, genetic testing, and immunophenotyping.

## CT
CT scan may be helpful in the diagnosis of follicular lymphoma.

## MRI
MRI may be helpful in the diagnosis of follicular lymphoma.

## Ultrasound
There are no ultrasound findings associated with follicular lymphoma.

## Biopsy
Lymph node or extranodal tissue biopsy is diagnostic of follicular lymphoma.

## Other Imaging Studies
PET scan may be helpful in the diagnosis of follicular lymphoma.

## Other Diagnostic Findings
Other diagnostic studies for the diagnosis of follicular lymphoma include bone marrow aspiration and biopsy, laparoscopy, and laparotomy.

# Treatment

## Medical Therapy
The optimal therapy for follicular lymphoma depends on the stage at diagnosis, age, and prognostic scores. The predominant therapy for follicular lymphoma is chemotherapy. Adjunctive hematopoietic stem cell transplantation, and radioimmunotherapy may be required.

## Surgery
Surgical intervention is not recommended for the management of follicular lymphoma.