Quiz: March 2006


This one-year-old baby was referred for a solitary nodular lesion that he has had since 4 months of age. He had not any other significant medical problem. Skin biopsy showed an infiltration of closely packed cuboidal cells in the dermis.

What is your diagnosis? 




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Diagnosis: Solitary mastocytoma

Comment by; M. Mehravaran, MD, Dermatologist/ Szeged, Hungary:

The term mastocytosis encompasses a group of clinical disorders that result from an abnormal proliferation of tissue mast cells in variety of tissues in particular in skin. Mastocytosis occurs in all races and affects both sexes equally. The peak incidence of mastocytosis is in children, in over half of all patients the disease is diagnosed before the age of 6 months (as in Quiz case). There is second peak of incidence in young adult. Mastocytosis tends to be transient in children and chronic in adults
Two subgorups of mastocytosis patients are recognized: those with only skin involvement (cutaneous mastocytoma) and those with mast cell infiltrates involving several different organs (systemic mastocytosis).
Patients with cutaneous mastocytosis can be generally classified into:
  • solitary mastocytoma,
  • urticaria pigmentosa,
  • diffuse or erythrodermic mastocytosis,
  • telangiectasia macularis eruptiva perstans.
The number of mast cells infiltrating the dermis in cutaneous mastocytosis varies from a relatively small number that is undetectable on the physical examination to larger aggregations forming papules, nodules, or diffuse thickening of the skin. Papular or nodular lesions with dense dermal infiltrates may have a yellowish hue that accentuated by diascopy. Darierís sign, which is development of urtication and delayed, axonally mediated erythematous flare, can usually be elicited by rubbing or other minor trauma to a lesion. Such physical stimulus causes mast cell degranulation with the release of mast cell mediators and local tissue effects of vasodilatation, increased vascular permeability, and edema. Generally other changes include hyperpigmentation, flushing, localied or generalized pruritus, occationally tense bullae in infants. Unususal severe complications in infancy include hypotension and shock, severe diarrhea and dehydration, and very rarely a bleeding diathesis.


The term mastocytoma has used to described nodular infiltrates (as in Quiz case) of mast cells occurring single or one of several isolated lesions. Solitary mastocytomas occur almost exclusively in the first 2 years of life and are often present at birth. These solitary nodules typically are found on the trunk and extremities and range in size from 5-60 mm in diameter. Darierís sign, epidermal pigmentation, the formation of vesicles and bullae, and localized flushing are common; generalized flushing has rarely been reported.
Lesions that are truly solitary usually regress completely or become asymptomatic and rarely persist into adulthood.
Histologically the infiltrating mass cells are usually monotonus and have round or oval, darkly staining, bland nuclei and a moderate amount of finely granular cytoplasm that gives the cells a distinctive appearance like a fried egg.


Most solitary mast cell lesions resolve spontaneously, generally no treatment is required. Therefore are self-limited and not-threatening, reassurance of the usual benign course of this disease and avoidance of specific factors known to trigger mast cell degranulation such as immunologic (allergens), physical (heat, cold, sunlight, trauma), biologic toxins (snake, insect, jellyfish and shellfish) and drugs (aspirin, alcohol, narcotics). Excision of symptomatic solitary mastocytomas may rarely be indicated, e.g., if severe cardiovascular or respiratory symptoms are being produced.
Since no effective therapy exists for controlling mass cell proliferation, treatment for the remaining subgroups of mastocytosis patients is directed at inhibiting the local (Potent topical corticosteroids) and systemic effects of released mast cell mediators.

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