Ependymomas are tumors seen in older
children, iso- to hyperdense with punctate calcifications, small cysts,
and moderate enhancement on intravenous contrast.
Xanthogranulomas are benign choroid
plexus masses usually bilateral seen typically in older children, occasionally
in children. These tumors may attain strikingly large sizes.
Vascular malformations though not so
common in intraventricular sites may occasionally be seen in children.
PNETs seen mainly in the first decade
of life are tumors with heterogeneous masses with solid portions enhancing
variably, cystic areas and foci of punctate calcifications. Hemorrhage is
seen in 10% cases.
Teratomas are well- circumscribed benign
masses with both solid and cystic components, which on CT show mixed density
or homogenous mass enhancing variably on contrast study.
Astrocytomas are most often seen as
cystic lesions with tumor nodule within. There may be a speck of calcification
in the tumor nodule. There is marked post contrast enhancement.
Choroid Plexus Papillomas present early
in infancy with signs of raised intracranial pressure and in contradistinction
to all other causes mentioned above is associated with overproduction of
CSF. This leads to communicating well- compensated hydrocephalus. In this
case, a diagnosis of choroid plexus papilloma was considered as it was seen
in the trigone with a communicating type of hydrocephalus although cystic
type of CPPs are uncommon. CPPs are the only tumors, which secrete CSF leading
to hydrocephalus due to overproduction. PNET was considered the second differential,
however due to the presence of hydrocephalus of non-obstructive type it
was a less likely possibility.
Final Diagnosis:
Biopsy of the tumor showed a CHOROID PLEXUS PAPILLOMA.
Discussion:
Choroid Plexus Papillomas are large aggregations
of choroidal fronds that are microscopically similar to normal choroid plexus.
CPPs account for <1% of all primary intracranial tumors and 2-4% of childhood
intracranial tumors with a distinct male preponderance. They present during
infancy with signs of increased intracranial pressure due to overproduction
of CSF by the tumor.
These tumors are most commonly located in
the trigone of the lateral ventricles, bodies of lateral ventricle, third
and fourth ventricles. In the pediatric age group lateral ventricles are
the commonest sites with preponderance for the left side. The fourth ventricle
is the most common site for CPPs in adults, but is a rare site in pediatric
age group. Rarely, the tumor may be bilateral.
Seen mainly in infancy, these tumors are detected
because of the severe hydrocephalus. Grossly, these tumors are dark pink
or red globular masses with an irregular papillary surface resembling a
cauliflower, well defined and quite separate from the surrounding brain.
Small areas of hemorrhage may be present with multiple gritty foci of calcification.
Some CPPs show evidence of anaplasia and invasion
of adjacent brain. Anaplastic papillomas cannot be differentiated from carcinomas
based on gross pathologic features. The distinction is based purely on characteristics
of individual cells. Both aggressive papillomas and carcinomas show a marked
propensity to metastasise through the CSF pathways, sometimes forming large
subarachnoid masses.
Imaging features of CPP:
CT: Isodense
or mildly hyperdense to normal brain, with occasional punctate foci of calcification.
Homogenous enhancement occurs on intravenous contrast. Aggressive papillomas
have more irregular appearance, closely resembling a carcinoma, due to growth
through the ependyma into surrounding white matter inciting surrounding
edema.
MRI: CPPs are lobulated intraventricular
masses that tend to be homogenous on both T1 & T 2 weighted sequences. Typically
hypointence compared to gray matter on T 2 weighted images. Foci of calcification
or hemorrhage are occasionally present. Uniform intense enhancement follows
intravenous administration of paramagnetic contrast.
