CHOROID PLEXUS TUMOR

CHOROID PLEXUS TUMOR
These are papillary neoplasms  derived from choroid plexus epithelium and are
  • choroid plexus papilloma (WHO Grade I)
  • Atypical papillomas (WHO grade II)
  • Choroid plexus carcinomas (Grade IV)
Clinical features:
  • Commonly occur at birth or in children.
  • Lateral ventricles and less often 3rd ventricles are favoured in this age group.
  • In adults -4th ventricle is the common site.
  • Most of these lesions occur sporadically. Few cases are associated with Li-Fraumeni & Aicardi syndromes.
  • Ectopic neoplasms can occur in supraseller region, cerebelloportine angle & even the spinal epidural space.
  • Papillamas produce hydrocephalus due to the obstructions CSF flow.
Radiological findings:
  • Both papillomas and carcinomas are discrete, intensely contrast enhancing.
  • Tumors at cerebellopontine angle and above intraventricular region show cystic change and parenchymal edema.
  • Lobular or nearly papillary diagnostic architecture is present.
  • Tumors of the fourth ventricle may be heavily calcified.
  • Carcinomas are often cystic invasive.
Gross finding:
  • Papilloma are well circumscribed, lobular and in some cases overtly papillary lesion.
  • Both papilloma and carcinomas are highly vascular lesions.
Microscopic findings:
  • Choroid plexus tumors are graded depending upon the
    • Epithelial differentiation
    • Cytologic atypia
    • Mitotic activity
  • Transition of the neoplasm to normal choroid plexus is common but from papilloma to carcinoma is unusual.
  • Well differentiated tumors have on orderly layer of columnar epithelium on a basement membrane that overlies delicate fibrovascular stalks.
  • The surface of the more columnar crowded cells is linear or flatter when compared to cobblestone or hobnail appearance of normal choroid plexus
  • Choroid plexus papillomas
    • tend to have bland round to oval nuclei with very rare mitotic figures.
    • Cells are usually present in one layer over the vascular core.
    • Necrosis, vascular hyperplasia or invasion into brain parenchyma are absent.
    • Mostly all the tumor show papillary structure.
    • Acini or tubules can also be present.
  • Other features which can occur in papillomas are
    • Glial differentiation
    • Pigmentation
    • Oncocytic change
    • Calcification
    • Xanthomatous change
    • Bone
    • Cartilage
    • Extensive sclerosis
  • Atypical papillomas (WHO grade II) can be distinguished from grade I papillomas on the basis of mitotic activity -2 or more /10hpf.
  • Choroid plexus carcinomas
    • the tumor cells show architectural disarray with sheets, complex glands, cribriform arrangement and only poorly formed papillae.
    • Nuclear pleomorphism is prominent with abundant mitosis and necrosis.
    • Hyaline protein droplets may be present.
  • Tumor cells may have perinuclear resembling oligodendroglioma
  • Both papillomas and carcinomas can invade the brain parenchyma and does not affect the prognosis adversely.
  • Choroid plexus papillomas can disseminate in CSF pathway producing implants of benign papillomas over the leptomeninges of brain and spinal canal. Hematogenous metastasis outside the brain is criteria of malignancy
Immunohistochemistry findings:
  • Neoplastic cells are immunoreactive for
    • Vimentin
    • Cytokeratin
    • S-100 protein
    • Transthyretin
    • Synaptophysin
    • EMA (in some cases)
    • GFAP (focally)
Cytogenetics:
  • Choroid plexus papillomas have
    • Gains of chromosome 5, 7, 9, 12, 15&18
    • Loss of chromosome 21&22
  • Carcinomas have-
    • Gains of chromosomes 1, 4 &14
    • Loss of chromosomes 5,15& 18
Differential Diagnosis
  • Papillary ependymoma have both epithelial and non epithelial elements with fibrillary areas. Highly fibrillated areas are not seen in papillomas. Ependymomas lack prominent basement membrane. Ependymomas are widely GRAP positive.
  • Well differentiated metastatic carcinoma
    • IHC for BerEP4 and HEA 25 are positive in metastatic carcinomas and rarely positive in choroid plexus tumors.
    • Choroid plexus carcinomas are Synaptophysin positive where as metastatic tumors are negative
  • Atypical teratoid/Rhabdoid tumor – Solid non papillary variant of choroid plexus carcinoma resembles Atypical teratoid/Rhabdoid tumor. Choroid plexus carcinoma effects young children where as AT/RT presents in infancy. Rhabdoid lesions most often occurs in the posterior fossa, whereas almost all the choroid plexus carcinomas are supratentorial and intraventricular. Nuclei of choroid plexus carcinomas are positive for INI 1 protein whereas those AT/RT are not
  • Papillary endolymphatic sac tumor – These tumors occur at the cerebellopontine angle and arises in adults as a component of Von Hippel Lindaus syndrome. Epithelium is less papillary and simplar than plexus neoplasm.
Treatment and prognosis
  • Well differentiated tumors can be resected and cured without radiography or chemotherapy.
  • Carcinomas are invasive and are unresectable and therefore likely to recur.
  • They may disseminate through the CSF but rarely through haematogenous route.
  • Atypical papillomas are resected completely.
References
  1. Peter C.Burger, Bernd W. Scheithauer. Choroid plexus papilloma, Atypical papilloma, and Carcinoma.In: Tumors of the Central nervous system. AFIP Atllas of Tumor pathology series 4.177-208
  2. Douglas C. Miller. Choroid plexus neoplasms and Miscellaneous intracerebral masses.In: Modern Surgical Neuropathology. 195-205.