Papillary craniopharyngioma

Papillary craniopharyngiomas are WHO grade 1 tumors of the pituitary region typically presenting as mostly solid masses in adults. They are an entirely separate entity from the far more common adamantinomatous craniopharyngioma that are found at all ages but particularly in children ^1,2. 

Terminology

Until the 5^th Edition (2021) of the WHO classification of CNS tumors, papillary craniopharyngiomas were considered a subtype of craniopharyngiomas along with adamantinomatous craniopharyngioma ¹.

Increasing molecular evidence has demonstrated that they have distinct and mutually exclusive mutations of CTNNB1 (adamantinomatous) and BRAF (papillary) ^1-3. As such, they are now considered separate entities and are discussed separately. 

Epidemiology

Papillary craniopharyngiomas are far less common than adamantinomatous craniopharyngiomas and rare before middle age, identified most commonly between the ages of 40 and 60 years of age ^4,6. No sex or racial predilection has been identified ⁴. 

Importantly, even though adamantinomatous craniopharyngiomas are thought of as tumors of childhood whereas papillary craniopharyngiomas are considered tumors of adults, adamantinomatous craniopharyngiomas are more common than papillary craniopharyngiomas at all ages ^4,6. 

Clinical presentation

Clinical presentation is variable on account of the variable location and size of the tumor. Presenting complaints include:

• headaches and raised intracranial pressure
• visual symptoms
• hormonal imbalances
  • decreased libido
  • amenorrhea
  • diabetes insipidus

Pathology

Papillary craniopharyngiomas are formed of masses of monomorphic squamous epithelium with a fibrovascular core and scattered immune cells ³.

Unlike adamantinomatous craniopharyngiomas, "wet keratin" and calcifications are absent ⁵.

Although cysts do form, they are not a prominent feature, and the tumor is usually mostly solid ⁵. 

Radiographic features

Papillary craniopharyngiomas are primarily suprasellar tumors with a small intrasellar component is present in a minority of cases. A purely intrasellar location is uncommon. Occasionally, they appear as masses within the third ventricle ^5,6. 

Papillary craniopharyngiomas tend to be more spherical in shape and usually mostly solid or contain a few smaller cysts ^5,6. 

CT

• cysts
  • small and not a significant feature
  • near-CSF density
• solid component
  • soft tissue density
  • vivid enhancement
• calcification
  • uncommon/rare

MRI

• cysts
  • when present, they are variable in signal
  • T1: 85% are T1 hypointense ⁴
• solid component
  • T1: iso- to slightly hypointense to brain
  • T1 C+ (Gd): vivid enhancement
  • T2: variable/mixed 
• MR spectroscopy: cyst contents does not show a broad lipid spectrum as they are filled with aqueous fluid

Treatment and prognosis

Treatment is usually surgical with radiotherapy, especially useful for incomplete resection. The surgical approach depends on the size and sellar vs suprasellar extent. Some lesions can be accessed via a transsphenoidal approach, whereas others require a craniotomy. 

Prognosis is similar to that of adamantinomatous craniopharyngiomas, most affected by the age at diagnosis, with progressive worse prognosis with advancing age ^4,6. In children, the overall 3-year survival of all craniopharyngiomas is ~95% whereas it drops to ~45% for elderly patients >80 years of age ⁴.   

Differential diagnosis

General imaging differential considerations include:

• pituitary macroadenoma
  • can look very similar
  • usually has intrasellar epicenter with pituitary fossa enlargement rather than the suprasellar epicenter
• pituicytoma
• chordoid glioma
• meningioma