Choroid Plexus Tumors
Choroid Plexus Papilloma (WHO Grade I), Atypical Choroid Plexus Papilloma (WHO Grade II), and Choroid Plexus Carcinoma (WHO Grade III)
Altogether, tumors of the choroid plexus epithelium represent a very small fraction of all primary central nervous system (CNS) tumors, making up less than 0.5% (1). Papillomas are more common than carcinomas by a margin of at least 2:1 (2,3,4). The age range for reported choroid plexus neoplasms is broad, extending from 0 to 72 years, yet the distribution is strongly skewed toward early childhood, with a median age for all cases of 3.5 years in one extensive review of the literature (5). One large tumor registry dataset showed choroid plexus tumors (CPTs) to account for 2.3% of childhood brain tumors, and about 10% of those in infancy (6). Although older patients tend to get choroid plexus papillomas (CPPs) rather than higher grade lesions, the median ages for all three histologic grades were below 3 years in a recent large clinical series (4). Older patients also tend to have more caudally located tumors than the young. Nonetheless, those patients in the first decade remain common at every anatomic location (5). Males and females are roughly equally represented among cases of CPTs. Patients most commonly present with obstructive hydrocephalus due to their intraventricular growth.
Patients with Aicardi syndrome may have an increased risk for developing CPPs, some developing multiple simultaneous lesions (7). Other features of this cryptogenic syndrome include agenesis of the corpus callosum, infantile spasms, and chorioretinal lacunae.
Choroid plexus carcinomas (CPCs) have been noted to occur in the context of Li–Fraumeni syndrome, frequently in the setting of confirmed germline TP53 mutations (8,9). Although CPC is not particularly common among Li–Fraumeni-related cancers, it appears that Li–Fraumeni and Li–Fraumeni-like syndromes are more frequent in patients with CPC and even present in some children with CPP (10). Another series suggests that a significant number of CPT patients may have germline TP53 mutations without any family history (11).
Neuroimaging of CPTs shows a solid, well-circumscribed, contrast-enhancing mass that is sometimes internally cystic. An identifying feature, when present, is a multinodular, bosselated profile. CPTs are typically unifocal but can be either truly multifocal (7) or disseminated via metastases (12).
The most common locations for CPTs include all four ventricles and the cerebellopontine (CP) angle, that is, places where normal choroid plexus is found, although they have been reported to occur in extraventricular locales. The lateral and fourth ventricles contain the vast majority of CPTs. Both location and histologic grade correlate with age; adults tend to get papillomas and these are common in the fourth ventricle, whereas children tend to have higher grade lesions that arise in the lateral ventricles (5).
The primary treatment approach for all CPTs is surgical resection, with the frequent addition of chemotherapy for carcinomas. Radiation therapy also seems to have benefit, but its role in the treatment of CPC and atypical choroid plexus papilloma (ACPP) is still being examined (12). Because of the rarity of these malignancies, treatment regimens are varied and standard approach has yet been determined. Grade I papillomas are essentially cured by gross total resection, with one series reporting 100% 5-year survival without recurrence, the rate dropping to 68% with subtotal resection (13). CPCs, in contrast, are aggressive and have 5-year overall survival rates around 60%, although long-term cures have been achieved after complete resection (14).
All grades of choroid plexus neoplasia have the potential to metastasize, and it is most common for carcinomas to disseminate in the cerebrospinal fluid. Abdominal dissemination via ventriculoperitoneal shunt has been described (15).
Besides histologic grade, completeness of resection is an important prognostic factor for all CPTs. In CPCs, the presence of TP53 mutations is associated with much worse outcomes, 0% survival at 5 years in one series (16).
Papillomas recapitulate many of the features of normal choroid plexus; a field of branching fibrovascular cores sporting a monolayer of bland epithelial cells (Figure 11-1). The regularity and organization of most papillomas is on the level of a normal anatomic structure; however, the epithelial component is not formed of the short and bump-like “hob-nail” cells of normal choroid plexus (Figure 11-2) but cuboidal to columnar cells with a more smooth and contiguous surface (Figure 11-3). This vertical exaggeration can pull the nuclei into oblong conformations, yet they remain orderly and nonoverlapping.