DUAL CARCINOID EPITHELIAL NEOPLASIA OF THE APPENDIX

We report a series of 13 lesions of the human vermiform appendix in wh ich a carcinoid component was associated with a separate non-carcinoid epithelial component that included an adenoma-like lesion of the muco sal epithelium. We use the term dual carcinoid/epithelial neoplasia to describe this phenomenon. The carcinoid component was insular/trabecu lar in nine cases, tubular in one case and of goblet cell type in thre e. The epithelial component was a mucinous cystadenoma in four, a muci nous tumour of uncertain malignant potential in three, and a mucinous cystadenocarcinoma in six, No intermediate cell population was seen an d in three cases the carcinoid and epithelial components were in diffe rent parts of the appendix, leading us to suggest that these lesions m ay be true 'collision' tumours in which two neoplasms have arisen in t he same organ, The prognosis appears to be no worse than for either of the components alone, but conclusions regarding these lesions must be guarded on account oi. their rarity and the small numbers available f or study.