Clinical history: 5 year old female, sellar/suprasellar lesion.
What is the diagnosis, a differential of sellar/suprasellar lesions, and pathological features that help to distinguish between them?
The most common lesion in the sellar region of the brain is pituitary adenoma, however other lesions may also be encountered at this location, including:
craniopharyngioma (papillary or adamantinomatous)
rathke cleft cyst
Several of these entities involve cystic or partially cystic structures, and as with any cyst the key to evaluation is to determine the nature of the cells lining the cyst, and the cyst contents. For adamantinomatous craniopharyngioma, the lining cells show stratified squamous epithelium with peripheral pallisading and internal ‘stellate reticulum’ (loose textured epithelial cells). As with any cyst, compression can cause simplification and flattening of the lining cells, so examination of relatively protected areas are more helpful. The epithelium matures to ‘wet keratin’, which is amorphous partially cohesive collections of keratin debris, to be distinguished from the flaky keratin associated with an epidermoid cyst. The wet keratin can undergo dystrophic calcification. The cysts fluid is cholesterol rich with machine oil consistency. The surrounding glial tissue can show Rosenthal fibers.
Clinically craniopharyingioma is more common in the first decade, but also occurs in adults, especially the papillary variant which is almost exclusively seen in adults. The papillary variant is defined by its papillary architecture, and has none of the classic adamantinomatous features (stratified epithelium, wet keratin, machine oil fluid content).