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: MCT (mast cells with immunoreactivity for tryptase but not chymase) and MCTC (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 MCT-type and MCTC-type mast cell counts in lung adenocarcinomas. When analyzed according to Noguchi's classification, MCT-type and MCTC-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 MCTC-type but not MCT-type mast cells showed a significantly worse outcome than those in the low-count group in LBACs. Counting chymase-positive (MCTC-type) mast cells in tumor stroma may be a good prognosis predictor for LBACs, especially Noguchi type-C tumors.