Concurrent occurrence of gastric adenocarcinoma and duodenal neuroendocrine cell carcinoma: a composite tumour or collision rumours?

Background-Neuroendocrine cell (NEC) carcinoma is occasionally accompanied by adenocarcinoma but the relationship between these two morphologically di stinct tumours is unclear. Two hypotheses have arisen regarding the mechani sm for the association of adenocarcinoma and NEC carcinoma. One is that bot h are derived from a common multipotential epithelial stem cell. The second hypothesis is that adenocarcinoma and NEC carcinoma arise from a multipote ntial epithelial stem cell and a primitive NEC, respectively. Aims-To elucidate the relationship between the two histologically distinct tumours, adenocarcinoma of the stomach and NEC carcinoma of the duodenum. Patient/methods-We present a case in which the tumour extended across the p yloric ring, the gastric portion of which revealed adenocarcinoma while the duodenal portion showed argyrophil NEC carcinoma. The two histologically d istinct lesions of the tumour were examined by immunohistochemistry and gen etic analysis of p53. Results-The gastric region was negative for chromogranin A staining but pos itive for carcinoembryonic antigen (CEA) staining. In contrast, the duodena l region was positive for chromogranin A but negative for CEA. All tumour r egions showed a point mutation in p53 gene at exon 7 (GGC (glycine)--> GTC (valine) at codon 245). The distal portion of the duodenal tumour showed an additional point mutation in p53 gene at exon 5 (GCC (alanine)--> GTC (val ine) at codon 129). Conclusions-The two histologically distinct tumours, adenocarcinoma of the stomach and NEC carcinoma of the duodenum, appear to be derived from a comm on epithelial cell.