Lipid-Rich Neuroendocrine Tumors (“Carcinoids”) of the Appendix: Potential Confusion with Goblet Cell Carcinoid
S Serra, R Chetty. University Health Network/University of Toronto, Toronto, Canada
Background: So-called clear cell change has been described in neuroendocrine tumors at several locations. Those associated with von Hippel Lindau disease are pathognomonically “clear” and the cytoplasmic appearance has been ascribed to intracytoplasmic lipid. However, lipid has not been demonstrated in all cases of clear cell carcinoid tumors. Such variants have not been described in carcinoid tumors of the appendix and cases with a prominent proportion of clear or more correctly, lipid-rich cytoplasm may bear a superficial resemblance to goblet cell carcinoid and/or signet ring adenocarcinoma.
Design: The computer records of the Department of Pathology, University Health Network, Toronto were searched from 2001 to 2009 for cases coded as appendiceal carcinoid tumors. Goblet cell carcinoid tumors were excluded for the purposes of this study.
Results: Seven of the 43 cases retrieved fulfilled the aforementioned criterion and were included for the purposes of this study. Seven cases, in 5 females and 2 males ranging in age from 22 to 65 years, were noted to have a population of lipid-rich and vacuolated clear cells accounting for 25% or more of the tumor population. The carcinoid tumors were incidental in all cases with 4 of patients presenting with appendicitis, 2 with concomitant mucinous cystadenocarcinomas of the appendix and 1 with an adenocarcinoma of the ascending colon. Morphologically, the tumors had a nested and trabecular pattern and were composed of an admixture of microvesicular and clear lipid-rich cells. There were no mitoses, areas of necrosis of lymphovascular invasion and all cases extended to the mesoappendix. All cases were positive for synaptophysin, chromogranin and serotonin but negative for inhibin. Three cases were examined ultrastructurally, and showed the presence of intracytoplasmic lipid and neurosecretory granules. None of the patients have shown evidence of recurrent disease.
Conclusions: The importance of recognizing this variant of carcinoid tumor in the appendix is to avoid confusion with goblet cell carcinoid tumors with or without a signet ring adenocarcinoma. The presence of multi-vacuolated, foamy and clear cells, some resembling signet ring or goblet cells, in otherwise classical carcinoid tumors is rare but should considered in this context in the appendix.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 54, Tuesday Afternoon