Although
choroid plexus papillomas (
CPP) and primary choroid plexus
carcinomas (
CPC) are rare
neoplasms of the central nervous system, they have been the subject of a number of immunohistochemical studies. To date, no unique or specific marker for these
neoplasms has been found, however. Normal choroid plexus is a major site of
transthyretin (TTR) synthesis, and recently this
protein has been proposed as a possible specific marker of choroid plexus differentiation in
tumors. In this study, we performed immunohistochemistry for TTR on 13
choroid plexus tumors (six
CPP and seven
CPC) and on 23
carcinomas metastatic to the brain, four of which had a papillary architecture. We also included four ovarian
teratomas that contained choroid plexus elements. Two of the
CPP had diffuse staining for TTR, while the four others stained only focally. Five of the
CPC stained only focally and less intensely than the control, while one case was negative. Only one
CPC stained as strongly and diffusely as normal choroid plexus. Two of the papillary and six of the nonpapillary
metastases had focal staining similar to that seen in the five focally positive
CPC. The choroid plexus elements of the ovarian
teratomas stained as strongly as the positive control. These findings indicate that TTR immunoreactivity is not restricted to primary
choroid plexus tumors. Furthermore, most choroid plexus
carcinomas stain only weakly or not at all. This limits the usefulness of TTR immunohistochemistry in the diagnosis of
primary choroid plexus neoplasms and in the distinction of
CPC from metastatic
carcinoma.