Clinicopathological and immunohistochemical study of 20 choroid plexus tumors: their histological diversity and the expression of markers useful for differentiation from metastatic cancer.

The aim of this study was to summarize the clinicopathological features and the histological diversity of choroid plexus tumors and to examine the expression of immunohistochemical markers that are useful for their differentiation from metastatic cancer. Twenty cases were collected, including 11 choroid plexus papillomas, 5 choroid plexus adenomas, 1 atypical choroid plexus papilloma, and 3 choroid plexus carcinomas. The choroid plexus papillomas showed various parenchymal and stromal changes: focal solid growth, oncocytic alterations, melanin deposition, calcification, ossification, and xanthogranulomatous reactions. The choroid plexus tumors showed the following cytokeratin (CK) 7 and 20 staining patterns: CK7(+)/CK20(+) (11/19 cases), CK7(+)/CK20(-) (7/19 cases), CK7(-)/CK20(-) (1/19 cases), and CK7(-)/CK20(+) (0/19 cases). Positivity for CK5/6 and thyroid transcription factor-1 was found in 3 of 18 and 1 of 19 cases, respectively. All cases were negative for the estrogen receptor (0/18 cases). The choroid plexus tumors showed various CK7/CK20 staining patterns, and the staining of CK7 and CK20 in most CK7(+)/CK20(+) and CK7(+)/CK20(-) cases was focal, in contrast to that observed in carcinomas. Therefore, nondiffuse staining of CK, rather than the CK7/CK20 panel itself, is important for discriminating between a choroid plexus tumor and metastatic cancer.