Overlapping Immunohistochemical Features of Adenocarcinoma of the Nonpigmented Ciliary Body Epithelium and Renal Cell Carcinoma

PURPOSE: To find immunohistochemical markers that distinguish adenocarcinoma of the nonpigmented ciliary epithelium (NPCE) from metastatic carcinoma, espe-cially metastatic renal cell carcinoma.DESIGN: Retrospective case series.METHODS: Three cases of adenocarcinoma of the NPCE were examined histologically with hematoxylin-eosin stain and immunohistochemical stains including vimentin, AE1/AE3, Cam 5.2, CK7, PAX2, PAX8, AMACR, and CAIX. We also reviewed previously re-ported cases of this tumor.RESULTS: We found that the immunohistochemical profile of adenocarcinoma of the NPCE can overlap with renal cell carcinoma. Both tumors can express vi-mentin, cytokeratin AE1/AE3, Cam 5.2, PAX2, PAX8, and AMACR. One of the adenocarcinomas of the NPCE in our series also expressed CD10 and the renal cell carcinoma marker (RCC Ma). Carbonic anhydrase IX (CAIX) was not detected in any of the 3 tumors.CONCLUSIONS: Adenocarcinomas arising in phthisic eyes can be diagnostically challenging. We have found it particularly difficult to distinguish adenocarcinoma of the NPCE from metastatic carcinoma, especially metastatic clear cell renal cell carcinoma and papillary renal cell car-cinoma. Because of the immunophenotypic overlap, most patients will require systemic workup including imaging of the kidneys to be certain of the diagnosis. (C) 2021 Elsevier Inc. All rights reserved.