Diagnostic Value of Immunostaining for Tryptase in Patients With Mastocytosis

Abstract

The term "mastocytosis" is used to describe a heterogeneous group of disorders characterized by abnormal growth and accumulation of mast cells(MCs). Cutaneous and systemic variants exist. Systemic mastocytosis may show an indolent or malignant clinical course. In malignant mastocytosis (MM), the diagnosis often is missed because the MCs are morphologically abnormal and lack metachromatic granules or the underlying histologic picture is complex. The cytoplasmic serine protease tryptase is produced by MCs and is thought to be expressed at all stages of MC maturation. To assess the diagnostic value of tryptase staining in mastocytosis, tissue sections from 93 patients with mastocytosis, including MM (n = 37), systemic indolent mastocytosis(n = 47), urticaria pigmentosa (n = 5), MC leukemia (n = 2), and solitary skin mastocytoma(n = 2) were stained with the antitryptase antibody G3. The results were compared with those of Giemsa and chloroacetate esterase (CAE) staining. Using antitryptase antibody G3, MC infiltrates were identified in all patients examined, including those with MM (37 of 37), and virtually all the neoplastic MCs (> 95%) appeared to react with G3. In MM, significantly fewer MCs were positive in Giemsa (54.5%; p 10% of neoplastic cells positive) was considerably lower with Giemsa (48.6%; p