Diagnostic criteria of classical carcinoids.

The classical (mid-gut) carcinoids of the intestinal tract display a characteristic light microscopic morphology. However, sometimes intestinal tumours are seen resembling carcinoids and differential diagnostic difficulties arise. In the present study silver stains and immunoreactivities to chromogranin A + B, cytokeratins and epithelial membrane antigen (EMA) were evaluated as diagnostic adjuncts in six classical carcinoids and six intestinal carcinomas with carcinoid-like features. All classical carcinoids were argentaffin and argyrophil and contained a majority cell population with chromogranin immunoreactivity while only one carcinoid-like carcinoma was chromogranin-immunoreactive and the stained cells in that case represented a minority of the tumour cell population. The cytokeratins were shown to be non-discriminatory. However, EMA expression occurred in five intestinal carcinomas and in the majority of the tumour cells of four of these cases, while only one classical carcinoid displayed a few EMA positive cells. Thus, silver stains in combination with chromogranin A + B and EMA appears to be of value to discriminate between classical carcinoids and carcinoid-like intestinal carcinomas. Further when intestinal carcinoids and carcinoid-like carcinomas are diagnosed with the aid of various tumour markers both qualitative and quantitative considerations must be made.