Rathke's pouch is a small area that forms in the roof of the developing mouth. It eventually separates from the pharynx to form the anterior (ie: front most) portion of the pituitary gland. The pituitary gland sits in a bony enclave known as the sella turcica.
Remnants of Rathke's pouch can form craniopharyngiomas that typically lie above the sella turcica (ie: "supra-sellar"). In about a quarter of cases they also extend into the sella. Craniopharyngiomas are divided into adamantinomatous and papillary sub-types depending on their pathologic appearance under the microscope.
Adamantinomatous craniopharyngiomas are by far the most common type. They are the most common supra-sellar tumor in children; in addition, there is a smaller peak of cases seen in patients between 40 and 60 years of age.
Adamantinomatous craniopharyngiomas have cystic and solid components. The cystic component contains fluid that is rich in cholesterol crystals. The fluid resembles motor oil in consistency and color. The solid components have a large amount of stratified and keratinized squamous epithelium. Large conglomerations of keratinized material known as "wet keratin" may also be seen. Cystic degeneration and calcification is common.
Papillary craniopharyngiomas are more common in adults between the ages of 40 and 60. They are less likely to have cystic components and are rarely calcified. Pathologically they are composed of sheets of stratified squamous epithelium that form papillae like structures.
It is important to realize that craniopharyngiomas adhere to adjacent structures including cranial nerves, blood vessels, and brain tissue. Surrounding brain tissue may show intense gliosis with Rosenthal fibers. When this is seen in isolation it can be misdiagnosed as a pilocytic astrocytoma, which is another common brain tumor in children.
Craniopharyngiomas of either type present with disturbances in vision, as well as the signs and symptoms of hormone deficiency.
Most craniopharyngiomas are diagnosed after someone complains of vision loss. Temporal field cuts are common if the optic chiasm is compressed by the tumor.
Craniopharyngiomas can also compress the hypothalamus, pituitary gland, and pituitary stalk (aka: the infundibulum). This can result in hormone deficiencies. Delayed puberty, hypothyroidism, central obesity, and central diabetes insipidus are commonly seen in patients harboring craniopharyngiomas.
Characteristic imaging findings on MRI and CT scans, especially in the right age groups, can support the diagnosis. However, definitive diagnosis can only be made at the time of surgical resection by an experienced pathologist.
The best treatment modality for craniopharyngioma is surgical removal. There is significant debate about whether removal of the entire tumor is necessary. Some centers will biopsy and decompress the cystic components of the tumor. If residual tumor is present then radiation is often prescribed to help prevent recurrence.
The main risk of surgery and radiation is damage to the surrounding structures. Permanent vision loss, stroke, and injury to the hypothalamus and pituitary gland are all possible. Many patient's require permanent hormone replacement.
Craniopharyngiomas are benign tumors that arise from Rathke's pouch. They come in two flavors: adamantinomatous and papillary. MRI and CT scans usually show a mixed cystic and solid mass sitting just above the sella turcica. Many patients present with vision loss and hormone deficiencies. Treatment is with surgical excision with or without adjuvant radiation therapy. In addition, hormone replacement therapy is commonly needed.
- Diabetes insipidus
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