Adenocarcinoma and atypical carcinoid: morphological study of a gastric collision-type tumour in the carcinoma-carcinoid spectrum.

We report the morphological features of an unusual cardial gastric tumour in a 72 year-old white man. Histologic examination revealed two adjacent, "side by side", but not merged, components: a poorly differentiated one and a typical moderately-differentiated gastric adenocarcinoma. Both components were also found in the metastatic lymph nodes. Histochemical (Grimelius) and immunohistochemical (neuron specific enolase, chromogranin A, synaptophysin) studies revealed the endocrine nature of the poorly differentiated component, which however, was not argentaffin and did not show immunoreactivity for specific endocrine substances. The neoplastic lesion was classified in the carcinoma-carcinoid spectrum as collision-type tumour. Our data suggest the double and independent origin of the two components.