However, considering that only 71% of our colorectal adenocarcinomas were FABP1 positive and the even lower frequency of FABP1 positivity in other gastrointestinal adenocarcinomas, a negative FABP1 staining cannot serve as evidence for a pulmonary origin of an adenocarcinoma in the lung. This evidence concerns the gene FABP1 and colorectal adenocarcinoma.