Pituitary metastases

Pituitary metastases are rare, and unless a systemic metastatic disease is already apparent, are often preoperatively misdiagnosed as pituitary adenomas

This article will discuss metastatic lesions affecting only the pituitary gland. For other intracranial metastatic locations, please refer to the main article on intracranial metastases

Epidemiology

The demographic of affected patients reflects that of underlying primary tumours, which are most frequently breast cancer in women and lung cancer in men; thus elderly patients are most commonly affected 1-2. Pituitary metastases account for a minority of all intracranial metastases, although the figures vary widely from publication to publication 1.  

Clinical presentation

Clinical presentation is variable but includes 1

  • hormonal dysfunction
    • diabetes insipidus
      • common: 29-71% 3
      • presumably due to the predilection for posterior pituitary involvement (see below)
    • panhypopituitarism
    • hyperprolactinaemia: disruption of the normal inhibition of prolactin release by dopamine
  • mass effect

Pathology

The most common primary malignancies to be found in the pituitary are breast cancer in women and lung cancer in men, presumably merely due to a large number of cerebral metastases from these two cancers 2. Many other primary tumours have also been described 3

It is interesting to note that the posterior lobe and the infundibulum of the pituitary gland are more frequently involved than the anterior lobe (although this may not be the case in breast cancer 3). Presumably due to the fact that the anterior pituitary receives its blood via the portal circulation rather than directly from the hypophyseal arteries 1

Radiographic features

Although larger lesions are visible on CT, appearing as enhancing soft tissue masses, MRI is the modality of choice for assessment of the pituitary region. 

MRI

Although all metastases to the pituitary (as is the case everywhere) start as microscopic deposits, they are usually encountered in two patterns:

  1. a mass arising from the pituitary fossa (similar to a macroadenoma)
  2. infundibular lesion

Small intrasellar masses are generally not identified, mainly because they are presumably asymptomatic and require targeted sequences that are not performed without indication. 

Sizeable mass

These masses typically involve both the intra and suprasellar compartments. As they are usually rapidly growing they have some features that are helpful in distinguishing them from pituitary macroadenomas: 

  • relatively normal size fossa (growth in a short period)
  • bony destruction rather than remodelling
  • dural thickening
  • dumb-bell shape as the diaphragma sella has not had time to be stretched
  • irregular edges
Infundibular lesion

Involvement of the infundibulum typically appears as nodular or irregular thickening and enhancement. The posterior pituitary bright spot may also be absent, either from interruption of the regular transport of neurosecretory granules down the infundibulum or due to concurrent infiltration of the posterior lobe.

Treatment and prognosis

Treatment is usually reserved for patients with symptomatic lesions (e.g. visual failure due to chiasmatic compression) or those in whom the diagnosis is not obvious (e.g. not known to have a malignancy, or thought to be in remission). Surgical decompression and biopsy in both cases can be carried out, although the overall prognosis and physical reserves of the patient need to be taken into account. 

Whole brain radiotherapy is also an option when the pituitary lesion is one of many cerebral metastases 3. The proximity to the optic chiasm usually makes radiosurgery impractical without leading to loss of vision 3

Prognosis is difficult to estimate as it will vary significantly depending on the systemic disease and the primary histology, although as a general ballpark figure a mean survival of approximately six months is in line with the published literature 3

Differential diagnosis

The differential diagnosis of pituitary metastases is broadly that of pituitary region masses, and generally can be narrowed depending on the morphology of the lesion. 

Solid and enhancing pituitary region masses has a differential which includes: 

Nodular thickening and enhancement of the infundibulum have a differential that includes 1


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Article Information

rID: 17912
Section: Pathology
Tag: endocrine
Synonyms or Alternate Spellings:
  • Pituitary metastasis
  • Metastases to the pituitary gland
  • Pituitary gland metastases
  • Pituitary gland metastasis
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    Case 1: from breast carcinoma
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    Case 2: from neuroendocrine tumour
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    Case 3: from lung adenocarcinoma
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    Case 4: from breast cancer
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    Case 4: from breast cancer
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