Diffuse cutaneous mastocytosis with multiple cutaneous mastocytomas. Report of a case with clinical, histopathological and ultrastructural aspects.

A patient with diffuse cutaneous mastocytosis, present since birth, developed several cutaneous mastocytomas without any symptoms after puberty. Although the histological picture of the tumours, showing nuclear atypia, mitotic figures and varying metachromasia of the granules, raises suspicion of systemic involvement, this has not appeared so far. The absence of symptoms could be due to the synthesis of an abnormal secretory product by the mast cells, which is supported by the absence of oedema and dilated blood vessels in the presence of extensive degranulation and by the unusual ultrastructural picture of the mast cell granules, i.e. little electron density with the almost complete absence of lamellar and crystalline structures.