ガストリン放出ペプチド前駆体が異常高値を示した肺定型カルチノイド

Typical Carcinoid of the Lung with Abnormal Elevation of Serum Pro-gastrin-releasing Peptide （ProGRP）

ガストリン放出ペプチド（gastrin-releasing peptide：GRP）は肺小細胞癌で高率に産生されていることが知られている．GRPそのものは血中において不安定であり，前駆体であるガストリン放出ペプチド前駆体（ProGRP）が血中で安定していることから，肺小細胞癌の腫瘍マーカーとして広く使用されている．一方，定型カルチノイドにおいてProGRPが高値を示したという報告はきわめて少ない．われわれは術前ProGRPが異常高値を示した肺定型カルチノイドの1例を経験したので報告する．

A 40-year-old male was referred to our hospital because of a nodular shadow detected in the left lower lobe with the tendency to increase gently. Because fluoro-2-deoxy-D-glucose （FDG） uptake was extremely low on a FDG positron emission tomography （PET-CT）, the tumor was highly suspected of the benign tumor. Five years later, a follow-up computed tomography （CT） showed the shadow to be enlarged. FDG uptake was changed to be high, and serum level of pro-gastrin-releasing peptide （ProGRP） was extremely elevated. Surgical treatment was chosen under suspicious diagnosis of neuroendocrine tumor, such as small cell carcinoma, large cell neuroendocrine carcinoma, and carcinoid. By the intraoperative aspiration cytology, a small cell carcinoma or a carcinoid was suspected and left lower lobectomy with systemic lymph node dissection was performed. The final histological diagnosis was a typical carcinoid. The elevated serum ProGRP immediately decreased to normal postoperatively.