Mast cell tumor overview

# Overview
Mast cell tumor is a rare and heterogeneous disease characterized by the presence of excessive numbers of mast cells in various organs, mainly the skin and the bone marrow that manifests with an unusually broad spectrum of clinical and morphological appearances. Based on the affected organ(s), mast cell tumor may be classified into either cutaneous mastocytosis or systemic mastocytosis. Mast cell tumor may be classified into seven subtypes based on WHO classification system. Cutaneous mastocytosis is more common in children and the disease manifest itself in the first year of life in over 80% of cases. There is no sex predilection and race predilection to the mast cell tumor.  Mast cell tumor arises from the mast cell, which is a type of white blood cell involved in the inflammatory process. The progression to mast cell tumor usually involves the uncontrolled stimulation of the receptor for stem cell factor following mutation of C-kit cell surface receptor. On microscopic histopathological analysis, mast cells in the superficial and mid dermis that are lymphocyte like with dense granular cytoplasm which tend to be more abundant around blood vessels is characteristic finding of mast cell tumor. Mast cell tumor must be differentiated from other diseases that cause flushing,such as: phaeochromocytoma and carcinoid syndrome. Mast cell tumor must be differentiated from other diseases that cause elevated serum tryptase levels and cytopenia, such as: myelodysplastic syndrome, primary myelofibrosis, essential thrombocythemia, and chronic eosinophilic leukemia. Common complications of mast cell tumor include episodes of anaphylaxis, osteoporosis, and progression to malignant mastocytosis or mast cell leukemia. The prognosis of mast cell tumor varies with the subtype, location, and extent of the tumor. The cutaneous mastocytosis is associated with the most favorable prognosis and mast cell leukemia is associated with poor prognosis. The diagnosis of systemic mastocytosis is based on the presence of one major criterion and one minor criterion or three minor criteria. Major criteria include the presence of multifocal dense infiltrates of mast cells observed in bone marrow sections or other extra cutaneous organs. Four minor criteria include the presence of >25% abnormal spindle-shaped mast cells in bone marrow and/or tissues, detection of Kit mutation at codon 816 in bone marrow or extracutaneous organ(s), the expression of CD2 and
CD25 surface markers in C-kit positive mast cells from bone marrow or other organs, and elevated serum tryptase levels >20 ng/mL. Physical examination for mast cell tumor include inspection for a large assortment of types of skin lesions, testing for dermatographism (Darier's sign), and palpating for hepatosplenomegaly and lymphadenopathy. Laboratory tests that may be helpful for diagnosis of mast cell tumor include complete blood count, serum tryptase levels, plasma and urinary histamine levels, and coagulation profile. Biopsy of affected organ may be performed to detect possible accumulation of mast cells in an involved tissue. Other imaging studies for evaluation of mast cell tumor include sonography of internal organs, gastroscopy and colonoscopy with biopsy, and DXA scan of bones. The mainstay of therapy for mast cell tumor is avoidance of triggering factors and symptomatic therapy. Chemotherapy is indicated for aggressive form of mast cell tumor.

# Historical Perspective
Mast cell activation was first described by Dr. Nettleship and Tay in 1869. Dr. Sezary and other french scientists reported the first case of mast cell tumor in 1936.

# Classification
Based on the affected organ(s), mast cell tumor may be classified into either cutaneous mastocytosis or systemic mastocytosis. Mast cell tumor may be classified into seven subtypes based on WHO classification system.

# Pathophysiology
Mast cell tumor arises from the mast cell, which is a type of white blood cell involved in the inflammatory process. The progression to mast cell tumor usually involves the uncontrolled stimulation of the receptor for stem cell factor following mutation of C-kit cell surface receptor. On microscopic histopathological analysis, mast cells in the superficial and mid dermis that are lymphocyte like with dense granular cytoplasm which tend to be more abundant around blood vessels is characteristic finding of mast cell tumor.

# Causes
There are no established causes for mast cell tumor.

# Differentiating Mast Cell Tumor from other Diseases
Mast cell tumor must be differentiated from other diseases that cause flushing,such as: phaeochromocytoma and carcinoid syndrome. Mast cell tumor must be differentiated from other diseases that cause elevated serum tryptase levels and cytopenia, such as: myelodysplastic syndrome, primary myelofibrosis, essential thrombocythemia, and chronic eosinophilic leukemia.

# Epidemiology and Demographics
Mast cell tumor is a rare disease and considered to be an "orphan disease" affecting 200,000 or fewer people in the United States. There are no definite data regarding the prevalence of mast cell tumor among the US general population. Cutaneous mastocytosis is more common in children and the disease manifest itself in the first year of life in over 80% of cases. There is no sex predilection and race predilection to the mast cell tumor.

# Risk Factors
Common risk factors in the development of mast cell tumor are age and mutation of C-kit receptor.

# Natural History, Complications and Prognosis
Common complications of mast cell tumor include episodes of anaphylaxis, osteoporosis, and progression to malignant mastocytosis or mast cell leukemia. The prognosis of mast cell tumor varies with the subtype, location, and extent of the tumor. The cutaneous mastocytosis is associated with the most favorable prognosis and mast cell leukemia is associated with poor prognosis.

# Diagnostic Criteria
The diagnosis of systemic mastocytosis is based on the presence of one major criterion and one minor criterion or three minor criteria. Major criteria include the presence of multifocal dense infiltrates of mast cells observed in bone marrow sections or other extra cutaneous organs. Four minor criteria include the presence of >25% abnormal spindle-shaped mast cells in bone marrow and/or tissues, detection of Kit mutation at codon 816 in bone marrow or extracutaneous organ(s), the expression of CD2 and
CD25 surface markers in C-kit positive mast cells from bone marrow or other organs, and elevated serum tryptase levels >20 ng/mL.

# Diagnosis

## Staging
There is no established system for the staging of mast cell tumor.

## History and Symptoms

## Physical Examination
Physical examination for mast cell tumor include inspection for a large assortment of types of skin lesions, testing for dermatographism (Darier's sign), and palpating for hepatosplenomegaly and lymphadenopathy.

## Laboratory Findings
Laboratory tests that may be helpful for diagnosis of mast cell tumor include complete blood count, serum tryptase levels, plasma and urinary histamine levels, and coagulation profile.

## Biopsy
Biopsy of affected organ may be performed to detect possible accumulation of mast cells in an involved tissue.

## Other Imaging Findings
Other imaging studies for evaluation of mast cell tumor include sonography of internal organs, gastroscopy and colonoscopy with biopsy, and DXA scan of bones.

# Treatment

## Medical Therapy
The mainstay of therapy for mast cell tumor is avoidance of triggering factors and symptomatic therapy. Chemotherapy is indicated for aggressive form of mast cell tumor.

## Surgery
Surgical intervention is not recommended for the management of mast cell tumor.