Introduction
A Mastocytoma is a mast cell tumor that derives its origin from myeloid stem cells present in the bone marrow. It is usually located in the connective tissues of the skin and mucous membrane. The mast cells contain cytoplasmic granules, which comprise histamines, amino acids, and other inflammatory cytokines that play an important role in allergic reactions.
The neoplastic proliferation of mast cell clones can cause localized and systemic clinical manifestations. Most patients have skin involvement in the localized types of disease. One or many extracutaneous organs are involved in the systemic involvement of the disease. The systemic form of the disease is more commonly seen in adults and is chronic in nature. While the localized form of the disease usually occurs in children.
What Is the Etiology of Mastocytoma?
The etiology of the disease is not completely known. It is believed that the presence of lesional cells leads to the secretion of increased levels of various growth factors and cytokines, which in turn stimulates the production of mast cells and melanocytes. The interleukins inhibit the apoptosis (death) of mast cells.
Genetic mutations in the c-kit gene are also believed to be responsible for inducing the activation of mast cell growth factor, which is also thought to induce the proliferation of abnormal mast cells.
What Is the Epidemiology of Mastocytoma?
The cutaneous or localized form of the disease primarily affects children up to two years of age. The systemic form of the disease is more commonly present in adults. They are rare tumors and usually appear solitarily. These rare round-cell tumors do not have any race or gender predilection.
What Is the Pathophysiology of Mastocytoma?
The mast cells usually accumulate to form a nodular or a maculopapular lesion. Degranulation of the lesional mast cells can occur by physical stimuli such as rubbing or pressure application on the lesion. This degranulation process, in turn, can induce the release of inflammatory prostaglandins, histamine, cytokines, and leukotrienes which are responsible for causing the skin and systemic manifestations in the patient.
What Are the Signs and Symptoms of Mastocytoma?
The tumor usually occurs as a single lesion on the skin of the back or wrist. They rarely occur in the lungs. Children also get affected by the disease in some cases. Usually, the lesions are of variable size and appear yellowish-brown flat, raised lesions or nodules. The lesions are usually painless but can be related to itching and redness. If the lesion is rubbed, the mast cells can get degranulated, thereby causing flushing of the face, scratching, and swollen skin. This phenomenon is known as Darier's sign which is unique to the disease. Blister formation is common in children under three years of age.
There are primarily four types of cutaneous mastocytosis with different clinical presentations:
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Urticaria pigmentosa.
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Mastocytoma.
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Diffuse cutaneous mastocytosis.
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Telangiectasia macularis eruptiva perstans.
1. Urticaria Pigmentosa- It is most commonly present. It presents as multiple reddish-brown flat or raised lesions that are symmetrically distributed over the back region and extremities. The mouth and mucous membranes are not involved. Itching and dermatographism (a condition in which light rubbing on the skin can cause raised, red lines over the scratched surface.) are usually present. Systemic involvement most commonly affects the bones (osteoporosis), liver (hepatomegaly), spleen (splenomegaly), and digestive tract (malabsorption).
2. Mastocytoma- It is a small brown or tan-colored, raised patch, almost exclusively present in children. The lesions appear usually at birth. The lesions usually occur solitary on the trunk, neck, and wrist region. Darier sign may usually be present.
3. Diffuse Cutaneous Mastocytosis- It is also usually present in younger children under three years of age. It usually occurs as a generalized yellowish-brown pigmentation of the skin. In infants, systemic involvement may be seen as having a poor prognosis.
4. Telangiectasia Macularis Eruptiva Perstans- It is the rarest form of cutaneous mastocytosis, usually seen in adults. It appears as reddish-brown flat lesions on the trunk and often presents with frequent blisters in infants.
How Is Mastocytoma Diagnosed?
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Physical Examination- The diagnosis usually depends on clinical examination.
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Serum Tryptase Levels- If the diagnosis is not certain, serum tryptase levels can be evaluated to identify the increased number of mast cells.
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Fine Needle Aspiration Cytology (FNAC)- FNAC of the lesion can also be done to evaluate the proliferation of mast cells.
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Surgical Biopsy- This test may be required to differentiate the tumor from well-differentiated to poorly differentiated.
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Ultrasound- Abdominal ultrasound can be performed to rule out organomegaly.
What Is the Treatment of Mastocytoma?
The treatment is primarily symptomatic. The treatment is aimed to minimize triggers of scratching, itching, temperature change, and dryness that may lead to the release of mast cells. Oral antiallergics and topical steroids are generally given to reduce the symptoms. Phototherapy (treatment with a special type of light) is sometimes used to relieve itching. Surgical therapy is preferred for systemic cases. Epinephrine is administered in cases exhibiting signs and symptoms of anaphylaxis.
What Is the Prognosis of Mastocytoma?
Mastocytoma of the skin has a good prognosis. Mostly, the lesions resolve within a few years. However, lesions that appear later in life usually persist for several years. The adult-onset disorder usually has a risk of malignant transformation.
Conclusion
Mastocytoma is a round-cell tumor of mast cells. Usually, diagnosis is based on clinical presentation. But in a few cases, where the diagnosis is uncertain, the doctor may advise certain other tests. The treatment is primarily symptomatic with a good prognosis seen especially in children. However, systemic involvement is seen in adult-onset disease.
