Craniopharyngioma

From Dog

Craniopharyngioma are a rare, usually benign, suprasellar germ cell cystic neoplasia of older dogs[1].

During embryogenesis, the anterior pituitary ascends from the pharynx via the cranio-pharyngeal ducts at the neck of Rathke's pouch. During development of the canine fetus, the duct narrows and eventually separates the vesicle of Rathke's pouch from the oral cavity. These cysts, which are lined with columnar ciliated epithelial cells and contain mucin, may undergo neoplastic changes in later life, involving the neurohypophysis, infundibulum and third ventricle.

In certain breeds such as the German Shepherd, craniopharyngiomas cause subnormal secretion of growth hormone, resulting in dwarfism.

These tumors in older dogs are often associated clinically with diabetes insipidus, hypothyroidism[2] and secondary thalamic Frohlich's adiposogenital syndrome[3].

Affected dogs often present with symptoms of weight loss, polyuria, polydipsia, episodic circling, seizures, sudden blindness and incoordination[4].

Clinical investigation usually reveals hyposthenuria, sinus bradycardia and increased concentration of protein in the cerebrospinal fluid.

Diagnosis is difficult as imaging with CT or MRI may not reveal a mass within the sella turcica, requiring hypophyseal biopsy or exploratory craniotomy.

Definitive diagnosis usually requires intraoperative or postmortem biopsy, verifying a location above the sella turcica and a histological presence of characteristic single or multiple cyst-like neoplasms. These tumour, often up to 3 cm in diameter, are usually arranged in solid sheets or separated into islands by thick bands of collagen. Squamous differentiation of tumour cells with keratin formation and a focus of osseous metaplasia are often found. Occasionally, tumour cells may be arranged in rosettes[5]. The cysts are lined by a single layer of cuboidal to low columnar epithelium and contained proteinaceous fluid with numerous cholesterol clefts.

A differential diagnosis would include lymphoma, hyperadrenocorticism, hypothalamic-pituitary trauma[6], dorsally expanding cysts, inflammatory granuloma, lymphocytic hypophysitis[7], congenital malformations such as empty sella syndrome and neoplasms such as xanthogranuloma, infundibuloma, pituitary adenocarcinoma[8] and metastatic tumors such as metastatic mammary carcinoma, lymphoma[9], malignant melanoma and pancreatic carcinoma.

Treatment has not been reported with this disease, although hypophysectomy would empirically be effective, but would be associated with a poor prognosis due to .

References

  1. Valentine BA et al (1988) Suprasellar germ cell tumors in the dog: a report of five cases and review of the literature. Acta Neuropathol 76(1):94-100
  2. Neer TM & Reavis DU (1983) Craniopharyngioma and associated central diabetes insipidus and hypothyroidism in a dog. J Am Vet Med Assoc 182(5):519-520
  3. Saunders, LZ & Rickard, CG (1952) Craniopharyngioma in a dog with apparent adiposogenital syndrome and diabetes insipidus. Cornell Vet 42(4):490-495
  4. Eckersley GN et al (1991) A craniopharyngioma in a seven-year-old dog. J S Afr Vet Assoc 62(2):65-67
  5. Hawkins KL et al (1985) Craniopharyngioma in a dog. J Comp Pathol 95(3):469-474
  6. Foley C et al (2009) Hypothalamic-pituitary axis deficiency following traumatic brain injury in a dog. J Vet Emerg Crit Care (San Antonio) 19(3):269-274
  7. Meij BP et al (2012) Lymphocytic hypophysitis in a dog with diabetes insipidus. J Comp Pathol 147(4):503-507
  8. Goossens MM (1994) Diabetes insipidus in a dog with an αMSH-producing pituitary tumor. Vet Q 16(1):61
  9. Nielsen L et al (2008) Central diabetes insipidus associated with primary focal B cell lymphoma in a dog. Vet Rec 162(4):124-126