Morphological, cytochemical and ultrastructural studies of a case of systemic mastocytosis.

: Morphological, cytochemical and ultrastructural studies of mast cells were carried out in a patient affected with systemic mastocytosis. Neoplastic mast cells showed morphological features between classic tissue mast cells and circulating basophils. They showed strong granule metachromasia after toluidine blue, faint positivity to Hotchkiss reaction, strong positivity to chloroacetate esterase, while they were negative to alkaline phosphatase. Ultrastructural observations showed heterogeneity of granules, most of which had homogenous fine dotted contents. The origin and linkage between mast cells and circulating basophils are discussed.