Craniopharyngiomas are benign, slow-growing sellar/suprasellar tumours arising from Rathke’s pouch remnants characterised by squamous papillary epithelium with areas of calcification, cysts and wet keratin, and a mixed solid-cystic mass compressing optic chiasm and hypothalamus. Calcification is typically seen in paediatrics.
Description
Craniopharyngiomas are benign, slow-growing tumours that originate from remnants of the Rathke’s pouch, a part of the embryonic nasopharynx that contributes to the development of the pituitary gland. Although histologically benign, they often behave aggressively due to their critical location at the base of the brain, close to important structures such as the hypothalamus and optic chiasm.
Pathogenesis
Craniopharyngiomas arise from the epithelial remnants of Rathke’s pouch. The transformation of these remnants into neoplastic cells leads to tumour formation.
Subtypes
There are two histological subtypes of craniopharyngioma, each with distinctive radiological features:
- Adamantinomatous Craniopharyngioma (ACP): The most common subtype, primarily occurring in children and adolescents. It is characterised by solid and cystic components, with the cysts often filled with a machine oil-like fluid due to high cholesterol content. Calcification is typically observed in these tumours.
- Papillary Craniopharyngioma (PCP): This subtype primarily affects adults and is less likely to have calcification or cystic components.
Epidemiology, Risk Factors & Associations
- Bimodal age distribution with peak incidences in children (5-14 years old) and adults (50-74 years old).
- No significant gender predilection.
- No established risk factors.
Clinical Features
Patients may present with symptoms related to mass effect, including headaches, visual disturbances, and hormonal imbalances (such as growth retardation in children due to pituitary dysfunction).
Complications
Complications include visual loss, hypothalamic obesity, and other endocrine abnormalities due to mass effect on adjacent structures.
Pathological Features
Histopathology
- Macroscopic: Usually midline lesions that are solid, cystic, or a mixture of both. Calcifications are common, especially in ACPs.
- Microscopic: ACPs have squamous epithelium with “wet keratin” and palisading basal cells. PCPs show well-differentiated squamous epithelium without wet keratin or palisading basal cells.
Radiological Features
General Features
- Characteristically demonstrates a cystic and/or solid mass in the suprasellar region, often with calcifications (found in up to 90% of paediatric cases).
- ACPs often demonstrate both solid and cystic components
- PCP typically appears solid and homogeneous.
- Craniopharyngiomas can cause enlargement of the sella turcica and may extend into the third ventricle, causing obstructive hydrocephalus.
CT
- Non-contrast: Hyperdense compared to brain parenchyma, with calcifications typically seen in ACPs.
- Contrast-enhanced: Shows strong, sometimes heterogeneous enhancement of the solid components.
MRI
- T1: The solid components are typically iso- to hypointense relative to grey matter, while cystic components show variable signal intensities depending on their contents. High T1 due to high protein content.
- T2: The solid components are iso- to hyperintense, while the cystic parts appear hyperintense.
- T1 C+: Heterogenous enhancement of the solid components. Cysts walls may enhance.
- DWI/ADC: No significant diffusion restriction.
NM
- PET FDG: Uptake usually low, reflecting the slow-growing nature of these tumours.
Grading and Staging
Craniopharyngiomas are histologically benign World Health Organisation (WHO) grade I tumours.
Diagnosis
Diagnosis is typically established by radiographic features and confirmed with histopathological examination following surgical resection or biopsy.
Differential Diagnosis
- Rathke’s Cleft Cyst: Typically cystic mass with intracystic nodule which may enhance.
- Pituitary Macroadenoma: Usually located within the sella turcica, shows intense and homogeneous enhancement on post-contrast images.
- Meningioma: Typically shows intense homogeneous enhancement with a dural tail.
Management
- Surgical resection is the mainstay of treatment for symptomatic craniopharyngiomas.
- Complete resection can be challenging due to the close proximity of critical structures.
- Adjuvant radiotherapy may be employed in cases of incomplete resection or recurrence.
- Endocrinological assessment and management are often necessary due to the tumour’s impact on the pituitary gland and hypothalamus.