= malignant primitive germ cell neoplasm
Incidence: 1–2% of all cranial neoplasms
Age:<20 years in 90%
Histo: lymphocytes + large polygonal primitive germ cells; absence of capsule facilitates invasion
- Identical to testicular seminoma + ovarian dysgerminoma with the same radiosensitivity.
Location:
- pineal region (50–65%)
- suprasellar hypothalamic region (25–35%): infundibular stalk, floor of 3rd ventricle
- others: basal ganglia, thalamus
- synchronous locations in 10% of all intracranial germ cell tumors
- hyperattenuated mass on CT + reduced perfusion on DWI ← to abundance of lymphocytes
Cx: frequent CSF seeding (CSF cytology more sensitive than imaging like contrast MR of entire neuroaxis)
Rx: combination of irradiation (very radiosensitive) and chemotherapy (doxorubicin, cisplatin, cyclophosphamide)
Prognosis: 90% 5-year survival
Suprasellar / Hypothalamic Germinoma
Age: childhood + young adulthood; M = F
- hypothalamic symptoms:
- diabetes insipidus, emaciation
- precocious puberty frequent in children <10 years of age (tumor may be small / radiologically invisible)
- homogeneous well-marginated round solid mass
- prompt homogeneous contrast enhancement
MR:
- iso- to hypointense to gray matter on T1WI
- iso- to slightly hyperintense on T2WI ← diminished free water content
- absence of hyperintense posterior pituitary lobe ← blockage of infundibulum by mass
= DYSGERMINOMA = ATYPICAL TERATOMA = PINEALOMA (former inaccurate names)
- “pinealoma” = misnomer as it refers to any pineal mass
Incidence: 1–2% of all cranial neoplasms; most common pineal tumor (>50% of all pineal tumors, 66% of pineal germ cell tumors)
Age: 10–25 years (90% <20 years old); M÷F = 10÷1
May be associated with: ectopic pinealoma = secondary focus in inferior portion of 3rd ventricle
- Parinaud syndrome
- ± hydrocephalus ← compression of aqueduct of Sylvius
- well-defined lesion restricted to pineal gland
- may infiltrate quadrigeminal plate / thalamus
CT:
- sharply circumscribed hyperattenuating mass ← highly cellular lymphocyte component
- mass engulfs pineal calcifications
- moderate / marked uniform contrast enhancement
MR:
- round / lobular well-circumscribed relatively homogeneous mass iso- to hyperintense to gray matter on T1WI and T2WI ± cystic components
- reduced perfusion on DWI ← highly cellular lymphocyte component
- avid homogeneous Gd-DTPA enhancement
Cx: common invasion of adjacent brain + dissemination by CSF requires imaging of the entire neuroaxis!
Prognosis: good ← lesions highly responsive to radiation therapy with ≥90% 5-year survival
DDx: primary pineal neoplasm