Pituicytoma

Pituicytomas are rare tumours arising from pituicytes, a specialised glial cell in the neurohypophysis and infundibulum of the pituitary gland.

There is much confusion in the literature as to what exactly a pituicytoma is, with the term used to synonymously particularly in older literature by some authors for a number of other tumours, now recognised to be separate lesions, including 1,3-4:

Peak Incidence is in the 5th decade, with no cases less than 20 years old. There is a recognised female predilection with M:F ratio of 1:2.

Clinical presentation is either from endocrine dysfunction (amenorrhea, galactorra, infertility, diabetes insipidus, panhypopituitarism) or from compression of adjacent structures, typically the optic chiasm. Many are asymptomatic, with the lesion only found incidentally.

Pituicytomas are considered WHO Grade 1 tumours and are usually indolent.

Macroscopically these tumours are well circumscribed, soft to medium consistency with a gray to yellow homogeneous or granular cut surface. Necrosis and cystic degeneration are uncommon.

Histologically they are fibrillary astrocytomas, with rich blood supply. The cells are spindle or stellate in shape and syncytial fibrillary cytoplasm 1. They stain diffusely for S-100 and vimentin. GFAP and EMA are variably positive 1. Ki-67 is usually less than 2% 1.

CT

Typically these masses are homogeneously enhancing, either with the pituitary fossa or in the suprasellar region. Size is variable, ranging from a few millimetres to a few centimetres.

MRI
  • T1: isointense solid mass; posterior pituitary bright spot often absent
  • T1 C+ (Gd): bright contrast enhancement
  • T2: heterogeneous, hypointense to isointense
DSA

Pituicytomas have a rich capillary network, accounting for their usual contrast enhancement and propensity to bleed at surgery. They receive their blood supply form the normal and extensive supply to the pituitary gland, including the meningohypophyseal trunk and superior hypophyseal arteries.

As the tumours are benign and slow growing, if asymptomatic then expectant management is sufficient. If mass effect is present then resection may be required. Caution should be exercised as these tumours are highly vascular which may lead to difficulties with a routine transphenoidal approach.

Complete resection can be difficult due to the structures involved and local recurrence is common 1.

The differential is essentially that of a pituitary region mass, or more specifically a solid and enhancing pituitary region mass, which includes:


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Article Information

rID: 1887
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • Infundibuloma
  • Pituitary astrocytoma
  • Astrocytoma of the posterior pituitary

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