Chymase-positive mast cells in small sized adenocarcinoma of the lung

Mast cells accumulate in angiogenesis-dependent situations of lung adenocarcinoma. Human mast cells are divided into two major subsets: MC_T (mast cells with immunoreactivity for tryptase but not chymase) and MC_TC (reactive for tryptase and chymase). Chymase is an important mediator of tissue remodeling, but research into chymase-containing mast cell subpopulations has been hampered by the lack of reagents suitable for use with formalin-fixed tissue. We stained chymase using CC1 antibody in 66 cases of small sized lung adenocarcinoma as well as CD34 and tryptase. There were significant positive correlations of microvessel counts with MC_T-type and MC_TC-type mast cell counts in lung adenocarcinomas. When analyzed according to Noguchi's classification, MC_T-type and MC_TC-type mast cells were significantly increased in Noguchi type-C tumors localized bronchioloalveolar carcinoma (LBAC) with active fibroblastic proliferation] compared with in Noguchi type-A (LBAC) plus type-B tumors (LBAC with alveolar collapse). Members in the high-count group of MC_TC-type but not MC_T-type mast cells showed a significantly worse outcome than those in the low-count group in LBACs. Counting chymase-positive (MC_TC-type) mast cells in tumor stroma may be a good prognosis predictor for LBACs, especially Noguchi type-C tumors.