Combined neuroendocrine tumor and goblet cell adenocarcinoma of the appendix: a distinct entity? Insights from three new cases.

We report three new cases of combined neuroendocrine tumor-goblet cell adenocarcinoma of the appendix, submitted over a 15-year period to the French expert pathological network TENPath, in order to provide additional information about this exceptional tumor. There were two females and one male, aged 45, 55, and 68 years. All tumors were discovered incidentally. They formed well-limited nodules measuring 3.5 to 10 mm, containing two closely admixed components. The predominant component presented as a well-differentiated neuroendocrine tumor G1. The other component, recalling goblet cell adenocarcinoma, was made up of mucus-containing cells. Two tumors were limited to the appendiceal wall; one invaded the mesoappendix. No locoregional metastasis was found. Our findings compare well with the six previous cases reported in the literature, all of which had locoregional dissemination. They demonstrate that this rare composite tumor presents distinctive diagnostic and clinico-pathological features and may represent a distinct entity, requiring an adapted management.