DIAGNOSTIC-VALUE OF IMMUNOSTAINING FOR TRYPTASE IN PATIENTS WITH MASTOCYTOSIS

The term ''mastocytosis'' is used to describe a heterogeneous group of disorders characterized by abnormal growth and accumulation of mast c ells (MCs). Cutaneous and systemic variants exist. Systemic mastocytos is may show an indolent or malignant clinical course. In malignant mas tocytosis (MM), the diagnosis often is missed because the MCs are morp hologically abnormal and lack metachromatic granules or the underlying histologic picture is complex. The cytoplasmic serine protease trypta se 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, incl uding 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 we re compared with those of Giemsa and chloroacetate esterase (CAE) stai ning. Using antitryptase antibody G3, MC infiltrates were identified i n all patients examined, including those with NIM (37 of 37), and virt ually all the neoplastic MCs (> 95%) appeared to react with G3. In MM, significantly fewer MCs were positive in Giemsa (54.5%; p < 0.05) and CAE (78.8%: Ia < 0.05). Moreover, G3 produced clear diagnostic staini ng in all cases of MM, but the proportion of cases with clear diagnost ic results (> 10% of neoplastic cells positive) was considerably lower with Giemsa (48.6%; p < 0.05) and CAE (75.7%; p < 0.05) staining. By contrast, tryptase, Giemsa, and CAE produced diagnostic staining of MC s in virtually all cases of systemic indolent mastocytosis, urticaria pigmentosa, and solitary skin mastocytoma. In systemic mastocytosis, s urvival was significantly reduced in cases with Giemsa-/tryptase+ or C AE-/tryptase+ tumor cells compared to those cases with Giemsa+ or CAE MC infiltrates (p < 0.001).