A case of pulmonary papillary adenoma: possible relationship between tumor histogenesis/tumorigenesis and fibroblast growth factor receptor 2 IIIb.

Pulmonary papillary adenoma is a rare tumor. We analyzed a tumor which appeared in a 16-year-old Japanese woman. The tumor histologically showed papillary proliferation of one-layered tumor cells coating inflammatory fibrovascular cores. At the periphery of the tumor, the tumor cells grew in a lepidic fashion. The tumor cells were confirmed as type-II pneumocytes with electron-microscope. In this study, using immunohistochemistry, in situ hybridization and real-time reverse transcription polymerase chain reaction, we examined the expressions and quantities of fibroblast growth factor 10 (FGF10), keratinocyte growth factor (KGF) and fibroblast growth factor receptor 2 (FGFR2) IIIb, based on the extent of their abilities of proliferation and differentiation of type II pneumocytes. The tumor cells expressed FGFR 2 and produced 350 times more FGFR2IIIb messenger RNA (mRNA) than did the nontumorous lung. The quantity of KGF mRNA in the tumor tissue was twice that of the nontumorous lung. Moreover, there was dysregulation of FGFR2IIIb transcription in the tumor. According to these findings, we expect overexpression of FGFR2IIIb to play an important role in causing tumor. Because FGFR is suspected to be connected with lung carcinoma, we also treat similar tumorigenesis via FGFR as carcinoma; complete resection of adenoma might be indicated.