Craniopharyngioma

Craniopharyngiomas are derived from remnants of the craniopharyngeal duct (narrowing which separates Rathke's pouch from the primitive oral cavity), and can occur anywhere along the infundibulum (from floor of the third ventricle, to the pituitary gland).

Epidemiology

There is a bimodal distribution, with the first peak between the ages of 10 - 14 years and the second peak in the 7th decade. 

Males are more often affected.

Histology

There are two main types of craniopharyngiomas:

• adamantinomatous (paediatric)
• papillary (adult)

Adamantinomatous

Adamantinomatous craniopharyngiomas, seen predominantly in children, consist of reticular epithelial cells which have appearances remenisant of the enamel pulp of developing teeth. Single or multiple cysts are present, filled with thick oily fluid which is high in protein, blood products, and/or cholesterol, creating the so called "machinery oil".   "Wet keratin nodules" are a characteristic histological feature. 

Calcification is usually present (90%)

Papillary 

The papillary subtype, seen in adults, is formed of masses of metaplastic squamous cells. "Wet keratin" is absent. Cysts do form, but these are less of a feature, and the tumour is more solid. 

Calcification is common (50%)

Location

Typically craniopharyngiomas are located in the suprasellar region or within the sella, which may be expanded. The tumour can expand in all directions, frequently distorting the optic chiasm, or compressing the midbrain with resulting obstructive hydrocephalus.

Occasionally, craniopharyngiomas appear as intraventricular, homogeneous, soft-tissue masses without calcification (papillary subtype)

Rare locations reported include: nasopharynx, posterior fossa, extension down the cervical spine.

Imaging findings

CT

Craniopharyngiomas typically appear as a heterogenous mass in the suptrasellar region.

Calcification and cysts are very common:

• Over all 80-87% of craniopharyngiomas are calcified.
• Adamantinomatous - 90%
• Papillary - 50%
• Cysts are seen in 70 - 75% of cases (more frequently in adamantinomas)

MRI

Imaging findings depend on the histological subtype and on the size and content of the cysts.

T1 signal intensity varies depending on cyst contents, and can appear hyperintense due to protein, blood products, and/or cholesterol (in the classic adamantinomatous type). In the papillary variety, solid components appear isointense on T1-weighted images.

Contrast enhancement is typical, wither thin enhancement of the cyst wall, or diffuse heterogeneous enhancement of the solid components.

T2 signal is high in both solid and cystic components, but is variable depending on content of fluid. On T2* weighted sequences, then calcification my be seen as areas of signal drop out and blooming.

MR angiography may demonstrate displacement of the A1 segment of the anterior cerebral artery.