Cutaneous Mastocytosis (CM)

General: Diagnosis requires both clinical findings and histological evidence of mast cell infiltration of the skin. Mastocytosis in general may occur at any age and is equally common in males and females; however, cutaneous mastocytosis is more common in children, with skin lesions usually appearing by 6 months, while in adults it usually appears in the third or fourth decade. There are three major forms/variants of CM:

• Urticaria Pigmentosa (UP, or Maculopapular Cutaneous Mastocytosis (MPCM))
• Diffuse Cutaneous Mastocytosis
• Mastocytoma of Skin

Clinical: All three forms of CM may urticate when stroked (this is known as Darier's sign), and most show epidermal pigmentation. The term urticaria pigmentosa is defined as those two features in combination, and has been used as a general term for all forms of CM.

Gross:

Microscopic:

Stains:

• Positive:
• Negative:
• Suggested, focused panel:

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Images:

Cases:



Systemic mastocytosis is more common after the third decade, with some reported trends of a slight female prediliction.