Pineal gland and germ cell tumours Flashcards
How common are pineal gland tumours?
Adult: 1% of brain tumours
- 30-40% germinoma
- 20% NGGCT
Children: 5% of brain tumour
- 50% germinoma
-30% pineal parenchyma tumour
What types of pineal parenchyma tumours are there?
Pineocytoma (Gr 1-2)
Pineal parenchyma tumour of indeterminate differentiation (PPTID)
Grade 2-3
Pineoblastoma Gr 4
How common is pineoblastoma?
Second most common type of pineal gland tumour after Germ cell tumour
Microscopic features of Pineocytoma
Uniform, small mature cells (resembling normal pineal cells) that grow primarily in sheets and often form large pineocytomatous rosettes
Round nuclei with fine chromatin
Lots of processes
No Mitotic activity
Ki67 <1%
What age group does Pineocytoma usually occur in?
Adults
Microscopic features of Pineal parenchyma tumour of intermediate differentiation (PPTID)
Diffuse sheet or large lobules of monomorphic round cells that appear more differentiated than in pineoblastoma.
Pleomorphic cells may be present
Mitotic activity low-moderate
Ki67 often >5%
Microscopic features of Pineoblastoma
- Resembles other primitive neuroectodermal tumours e.g medulloblastoma
- patternless sheets of small immature neuro-epithelial cells
- High N:C ratio
- Hyperchromatic
- Frequent mitoses
- Homer-wright rosettes
What is the natural hx of pienoblastoma
More common in children <5years
Aggressive
Invades nearby structures and spreads via CSF
High risk of craniospinal dissemination -50%
Treatment paradigm for pineocytoma
Treat like LG Glioma
Maximal safe resection
GTR —> observation
STR —> post op RT can be considered or observation with RT at time of progression (50-54Gy)
Treatment paradigm for Pineoblastoma
Treat like medulloblastoma
Maximal safe resection —> CSI 23.4-36Gy in 13-20# + tumour bed boost to 50.4Gy if <3yo or 54Gy if >3yo
CHT prior to CSI for young children or those with STR to try improve resection with a second look surgery
Enrolment on high risk MB COG trials
Epidemiology of germ cell tumour
-Peak age 10-12yo, majority <20yrs
- Rare in early childhood
- Younger tend to have NGGCT, older tend to have pure germinoma
- 3% of childhood CNS malignancies
Anatomy relating to intracranial germ cell tumours
Usually arise from the proximal 3rd ventricle and affect supratentorial midline structures e.g. pineal gland, hypothalamus, basal ganglions
Subependymal spread occurs near 3rd and 4th ventricle
What are the classifications of germ cell tumours
WHO classifies them as Pure Germinoma 2/3 vs non germinomatous germ cell tumour (NGGCT) 1/3
NGGCT further divided into:
- embryonal carcinoma
- endodermal sinus/yolk sac tumour
- choriocarcinoma
- teratoma
- mixed tumours
Prognosis of intracranial germ cell tumours
Pure germinomas:
Very favourable, 5year OS 95%
treatment sensitive, require less intense therapy
NGGCT:
More aggressive than Pure germinoma
Require multimodality treatment
5 year OS 90%
Why is surgery not used in intracranial germ cell tumour?
Surgery is often restricted to biopsy only as the morbidity and mortality of resection can near 20%
Treatment of non metastatic pure germinoma?
Induction chemo –> Whole ventricular irradiation + boost RT (NO CSI)
CHCT with 4 cycles carboplatin/etoposide –> 18-24Gy Whole ventricular irradiation with 12Gy/8# boost to suprasellar GTV
(if CR to chemo 18Gy WVI, if PR 24Gy)
(per ACNS1123)
What is the significance of whole ventricular irradiation in germ cell tumours?
Due to natural hx of germ cell tumours to have subependymal spread, along ventricular lining that may not be visible on MRI.
In prior studies of involved field RT alone, over 80% of failures were located in the periventricular region, supporting WVI as standard.
What is the treatment of metastatic (CSF+) germinoma?
Induction chemo –> WVI + boost RT + CSI
CHT with 4 cycles of carboplatin/etoposide –> WVI 18-24Gy + Supra seller GTV boost to 45Gy + CSI 24Gy/16#
(so same as non metastatic but with CSI and higher boost dose. fractionation is still 1.5Gy/#)
What dose per fraction is used in germinoma?
1.5#
Treatment of localised NGGCT
Induction chemo –> WVI/CSI + boost RT
(note- doses higher compared to germinoma)
Chemo 6x carbo/etoposide alternating ifos etop, then CSI to 36Gy with Suprasellar GTV boosted with 18GY/10# to 54Gy/30# (total dose)
What did the ACNS1123 show for NGGCT
Ommission of CSI in patients who responded to chemo and had WVI instead for NGGCT led to high rates of spinal failure
Treatment of metastatic NGGCT
Induction chemo –> CSI + boost RT
Chemotherapy 6 x carbo/etop, alt ifosfamide/etop; –>
CSI 36GY/20# + 18Gy/10# boost to GTV (total dose 54Gy/30#) + 9Gy/5# to bulky spinal mets (total dose of 45Gy/25#)
How might a tumour in the pineal region present?
Obstructive hydrocephalus due to compression of 3rd Ventricle
Increased ICP- headache, nausea+vomiting, papilloma, lethargy
Ataxia
Seizure
Behaviour changes
Parinaud syndrome-poor upward gaze, accomodation but abnormal light response due to pressure on superior colliculus
How might a supra sella tumour present?
Hypothalamic/pituitary dysfunction
- Diabetes insipidus due to reduced ADH
- Growth hormone abnormalities: delayed or precocious puberty
- Isolated GH deficiency
- Hypothyroidism
- Adrenal insufficiency
Ophthalmologic abnormalities
- usually bitemporal hemianopia
Classic triad: Diabetes insidious + precocious puberty + visual deficit.
