α-fetoprotein (AFP)-producing colorectal adenocarcinoma is rare and typically not well recognized. In the present study, 3 cases of AFP-producing colorectal cancer are described. All 3 of these cases demonstrated increased levels of blood AFP associated with disease progression. Only case 2 exhibited classical histological hepatoid features. Following immunohistochemical tissue staining, all 3 cases were observed to be positive for AFP expression. In addition, the expression of hepatocyte growth factor (HGF), c-Met receptor and the transcription factor c-Myc were identified to be associated with the expression of AFP. The 3 cases demonstrated resistance to multiple drugs, including epidermal growth factor receptor inhibitors, despite the presence of wild-type Kirsten rat sarcoma viral oncogene homolog (K-RAS; codons 12 and 13), neuroblastoma-RAS (codons 12 and 13) and B-Raf proto-oncogene, serine/threonine kinase (V600E). We propose that hepatoid histological features or a positive AFP finding by immunohistochemistry are sufficient for a diagnosis of AFP-producing colorectal adenocarcinoma. Furthermore, we speculates that autocrine HGF/c-Met activation may be capable of inducing the dedifferentiation of common adenocarcinoma cells, reverting them to a cancer stem cell state and producing AFP or hepatoid differentiation. Consequently, therapy targeted to the HGF/c-Met signaling pathway may potentially be effective for the treatment of AFP-producing colorectal adenocarcinoma.
Keywords: colorectal cancer; hepatocyte differentiation; α-fetoprotein.