A case of α-fetoprotein–producing pulmonary carcinoma with restricted expression of hepatocyte nuclear factor-4α in hepatoid foci: a case report with studies of previous cases

SummaryWe report a case of α-fetoprotein (AFP)–producing pulmonary carcinoma with studies for messenger RNA (mRNA) expression of hepatocyte nuclear factor (HNF)-4α, which is a transcription factor that is highly expressed in the process of liver development. The patient was a 64-year-old man with a pulmonary tumor in his left lower lobe. Serum AFP was 673 ng/mL. The microscopic analysis of the surgical specimen revealed a large cell neuroendocrine carcinoma with occasional hepatoid foci. The competitive reverse transcriptase polymerase chain reaction analysis revealed that HNF-4α mRNA was expressed on the order of 102- to 103-fold more abundantly than control pulmonary carcinomas and normal lung tissues. In addition, AFP and HNF-4α expression was restricted in hepatoid foci. Two previously reported cases of AFP-producing pulmonary carcinoma were also positive, whereas all 18 control pulmonary carcinomas were negative for HNF-4α. These findings suggest that aberrant expression of HNF-4α is implicated in the emergence or maintenance of hepatoid foci in AFP-producing pulmonary carcinomas.