The histogenesis of appendiceal carcinoid tumours.

Twenty-two appendiceal carcinoid tumours, comprising 10 classical carcinoids, six tubular carcinoids and six goblet cell carcinoids were examined by histochemistry and immunohistochemistry. All of the tumours showed evidence of neuroendocrine differentiation. Classical carcinoids were invariably intimately associated with S-100 protein positive cells, supporting an origin from sub-epithelial neuroendocrine cells. Both tubular and goblet cell carcinoids expressed cytoplasmic mucin and immunoglobulin A, and neither were associated with S-100 protein positive cells. These observations suggest that tubular and goblet cell carcinoids are derived from epithelial crypt stem cells.