Mucinous carcinoid and endometriosis in an inside-out appendix.

This is the first report of the simultaneous occurrence of mucinous carcinoid and endometriosis in an inside-out appendix. The literature concerning carcinoids, endometriosis and intussusception of the appendix is reviewed. The mucinous, or goblet cell carcinoid was positive for mucin, argentaffin and argyrophil stains. Paneth cells were present. Two and one-half years with no tumor recurrence suggest good prognosis as previously reported.