= TUMORS OF PINEAL PARENCHYMAL ORIGIN
Incidence:<0.2% of intracranial neoplasms
Histo: neuroepithelial neoplasm arising from pineocytes / their precursors
- similar imaging appearance
- peripheral displacement of preexisting normal pineal calcification (= “exploded pineal calcification pattern”)
= highly malignant tumor derived from primitive pineal parenchymal cells
Histo: unencapsulated highly cellular primitive embryonal neoplasm composed of diffuse sheets of small round cells with scant cytoplasm (similar to medulloblastoma, neuroblastoma, retinoblastoma) ±
- Homer-Wright rosettes (neuroblastic differentiation), or
- Flexner-Wintersteiner rosettes (retinoblastic differentiation)
Age: any age, most common in first 2 decades; M÷F = 1÷1
- usually large lobulated mass
- obstructive hydrocephalus in almost 100%
CT:
- poorly marginated iso- / typically hyperdense mass
- may contain dense tumor calcifications
- intense homogeneous contrast enhancement
MR:
- heterogeneous with solid portion iso- / moderately T1 hypointense on T1WI + iso- / mildly T2 hyperintense
- reduced perfusion ← increased cellularity
- dense heterogeneous Gd-DTPA enhancement
Cx: hemorrhage, necrosis, spread
Spread:
- direct extension posteriorly with invasion of cerebellar vermis + anteriorly into 3rd ventricle
- CSF dissemination (frequent) along meninges / via ventricles as most common cause of death
N.B.: common CSF dissemination → image the entire craniospinal axis!
Prognosis: 58% 5-year survival after resection
Pineal Tumor of Intermediate Differentiation (20%)
Age: any with peak in early adulthood; M <F
Histo: diffuse sheets of uniform cells + formation of small rosettes; low to moderate levels of mitotic activity + nuclear atypia
Prognosis: 39–74% 5-year survival after resection
= rare slow-growing unencapsulated tumor
Histo: low-grade small uniform mature pineal parenchymal cells with lobular architecture + pineocytomatous rosettes
Mean age: 38 years; M÷F = 1÷1
Size:<3 cm
CT:
- well-marginated slightly hyperdense / isodense mass
- dense focal tumor calcifications possible
- well-defined marked homogeneous enhancement
MR:
- well-circumscribed hypointense / isointense mass on T1WI + hyperintense on T2WI
- avid homogeneous / internal nodular Gd-DTPA enhancement
Cx: cystic changes: rare CSF dissemination
Prognosis: 86–100% 5-year survival after resection
DDx: pineal cyst (NO trabeculations, NO enhancement)
Trilateral Retinoblastoma (rare variant in 1.5–5%)
= uni- / bilateral ocular retinoblastomas + midline small cell tumor
- most frequently in the region of the pineal gland (= neuroectodermal pineal tumor = pineoblastoma)
- suprasellar region
Frequency: 6% of patients with bilateral disease
- usually family history
- Usually diagnosed 21 (range, 6–141) months after discovery of ocular tumor
- enhancing midline pineal mass
- isoattenuating relative to gray matter on CT
- isointense relative to gray matter on T1WI
Cx: intracranial / intraspinal leptomeningeal dissemination
Prognosis: mean survival up to 19 months