Pituitary macroadenoma

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Pituitary macroadenomas are the most common suprasellar mass in adults, and responsible for the majority of trans-sphenoidal hypophysectomies. They are defined as pituitary adenomas greater than 10 mm in size and are approximately twice as common as pituitary microadenomas

On imaging, they usually present as a solid tumour with an attenuation similar to the brain (30-40 HU) and demonstrates moderate contrast enhancement. The same is observed on MRI, where they are isointense to the grey matter both on T1- and T2-weighted images. However, attenuation and signal characteristics can significantly vary depending on tumour components such as haemorrhage, cystic transformation or necrosis.

For a general discussion, including epidemiology, treatment, and prognosis, please refer to the article on pituitary adenomas

Clinical presentation

Patients typically present with symptoms of local mass effect on adjacent structures (especially optic chiasm). Some may present hormonal imbalance, with symptoms of hypopituitarism (from compression) or secretion. Hormonal imbalance due to overproduction tends to present earlier and tumours are thus usually small at presentation. This mode of presentation is discussed in the article on pituitary microadenomas

Rarely pituitary apoplexy may present acutely and often catastrophically. 

Optic chiasm compression

The optic chiasm is located directly over the pituitary gland in 80% of individuals. The rest are divided between pre and post fixedpostfixed chiasms. A prefixed optic chiasm is located anterior to its normal position over the tuberculum sellae, whereas a postfixed chiasm is located over the dorsum sellae 10

A macroadenoma growing superiorly out of the pituitary fossa (or for that matter other pituitary region masses) will contact, elevate and compress the central part of the chiasm in most individuals. This central part carries fibres from the nasal retina, and thus results in the classical bitemporal hemianopia 10. Patients typically complain of bumping into things or having car accidents, but as the macular fibres are often spared, they may not be aware of actual visual deficits. 

In cases of prefixed or postfixed chiasms, or when the macroadenoma grows asymmetrically, then the optic nerves or optic tracts can be compressed, resulting in a variety of visual deficits. 

Cavernous sinus invasion

Some macroadenomas demonstrate invasive growth, and extension into the cavernous sinuses is characteristic. Prolactin secreting-secreting tumours are most frequently responsible for cavernous sinus extension, and typically prolactin level increase significantly when the tumour gains access to the sinus 10. Once in the sinus, these tumours are difficult to resect completely resect

They may compress cranial nerves resulting in deficits, although this is uncommon, seen in only 1-14% of cases 10. Oculomotor nerve (CN III) is most commonly involved, followed by the abducens nerve (CN VI) 10

Radiological and surgical invasion grading system characterised by areas distinguished from each other by a medial, median and lateral intercarotid lines: medial, lateral and central tangent on the intra- and supra cavernous internal carotid arteries on coronal view 11.

Pathology

Most macroadenomas are non-secretory (endocrinologically inactive). They are a type of benign epithelial tumour composed of adenohypophyseal cells

Radiographic features

Pituitary macroadenomas are by definition >10 mm mass arising from the pituitary gland, and usually extending superiorly. Indentation at the diaphragma sellae can give a snowman or figure eight configuration 10

CT

Non-contrast attenuation can vary depending on haemorrhagic, cystic and necrotic components. Adenomas which are solid, without haemorrhage, typically have attenuation similar to the brain (30-40 HU) and demonstrates moderate contrast enhancement; less marked than one typically sees in meningiomas. Calcification is rare.

MRI

MRI is the preferred imaging modality, not only able to exquisitely delineate the mass exquisitely, but also clearly visualise the optic chiasm, anterior cerebral vessels and cavernous sinuses. 

Overall signal characteristics can significantly vary depending on tumour components such as haemorrhage, cystic transformation or necrosis.

  • T1
    • typically isointense to grey matter 10
    • larger lesions are often heterogeneous and vary in signal due to areas of cystic change/necrosis/haemorrhage
  • T1 C+ (Gd)
    • solid components demonstrate moderate to bright enhancement
  • T2
    • typically isointense to grey matter 10
    • larger lesions are often heterogeneous and vary in signal due to areas of cystic change/necrosis/haemorrhage
  • GRE/SWI
    • most sensitive for detecting any haemorrhagic components, which appear as areas of signal loss
    • calcification is rare, but should be excluded by reviewing CT scans

Assessment of cavernous sinus invasion can be difficult. The most convenient method is to assess the degree of encasement of the cavernous portion of the internal carotid artery. Less than 90 degrees makes involvement of the sinus very unlikely, whereas greater than 270 degrees makes involvement almost certain 10

Nuclear medicine
PET-CT

Normal pituitary gland should not demonstrate significant FDG uptake and are normally not seen on PET-CT12. Pituitary macroadenomas are highly hypermetabolic both with FDG and Choline tracers.

Differential diagnosis

The differential of a pituitary macroadenoma is essentially the list of conditions leading to a pituitary region mass. The most common considerations include:

  • pituitary metastasis
    • often in the setting of known disseminated malignancy
    • often less well defined
    • bone destruction rather than remodelling may be seen
  • pituitary carcinoma
    • indistinguishable on imaging
    • CSF seeding may be evident
    • rare
  • meningioma
    • separate pituitary is usually identifiable 
    • dural tail usually visible
    • enhancement more vivid
    • hyperdense on non-contrast CT
  • craniopharyngioma (papillary type)
    • adamantinomatous craniopharyngiomas are more common in children
    • more likely to be cystic and to have areas of calcification (although still a minority of cases)
    • more likely to have areas of T1 intrinsic hyperintensity (although blood can result in similar appearances)
  • lymphocytic hypophysitis
    • common in peripartum female
  • saccular cerebral aneurysms 
    • flow void common on MR; CTA can show flow
    • more likely to have calcification
  • -<p><strong>Pituitary macroadenomas </strong>are the most common <a href="/articles/pituitary-region-masses">suprasellar mass</a> in adults, and responsible for the majority of trans-sphenoidal hypophysectomies. They are defined as <a href="/articles/pituitary-adenoma">pituitary adenomas</a> greater than 10 mm in size and are approximately twice as common as <a href="/articles/pituitary-microadenoma">pituitary microadenomas</a>. </p><p>On imaging they usually present as a solid tumour with an attenuation similar to brain (30-40 HU) and demonstrates moderate contrast enhancement. The same is observed on MRI, where they are isointense to the grey matter both on T1- and T2-weighted images. However attenuation and signal characteristics can significantly vary depending on tumour components such as haemorrhage, cystic transformation or necrosis.</p><p>For a general discussion, including epidemiology, treatment, and prognosis, please refer to the article on <a href="/articles/pituitary-adenoma">pituitary adenomas</a>. </p><h4>Clinical presentation</h4><p>Patients typically present with symptoms of local mass effect on adjacent structures (especially <a href="/articles/optic-chiasm">optic chiasm</a>). Some may present hormonal imbalance, with symptoms of hypopituitarism (from compression) or secretion. Hormonal imbalance due to overproduction tends to present earlier and tumours are thus usually small at presentation. This mode of presentation is discussed in the article on <a href="/articles/pituitary-microadenoma">pituitary microadenomas</a>. </p><p>Rarely <a href="/articles/pituitary-apoplexy">pituitary apoplexy</a> may present acutely and often catastrophically. </p><h5>Optic chiasm compression</h5><p>The <a href="/articles/supraoptic-recess-2">optic chiasm</a> is located directly over the pituitary gland in 80% of individuals. The rest are divided between pre and post fixed chiasms. A prefixed optic chiasm is located anterior to its normal position over the <a href="/articles/tuberculum-sellae">tuberculum sellae</a>, whereas a postfixed chiasm is located over the <a href="/articles/dorsum-sellae">dorsum sellae</a> <sup>10</sup>. </p><p>A macroadenoma growing superiorly out of the pituitary fossa (or for that matter other pituitary region masses) will contact, elevate and compress the central part of the chiasm in most individuals. This central part carries fibres from the nasal retina, and thus results in the classical bitemporal hemianopia <sup>10</sup>. Patients typically complain of bumping into things or having car accidents, but as the macular fibres are often spared, they may not be aware of actual visual deficits. </p><p>In cases of prefixed or postfixed chiasms, or when the macroadenoma grows asymmetrically then the <a href="/articles/optic-nerve">optic nerves</a> or <a href="/articles/optic-tract">optic tracts</a> can be compressed, resulting in a variety of visual deficits. </p><h5>Cavernous sinus invasion</h5><p>Some macroadenomas demonstrate invasive growth, and extension into the <a href="/articles/cavernous-sinus">cavernous sinuses</a> is characteristic. Prolactin secreting tumours are most frequently responsible for cavernous sinus extension, and typically prolactin level increase significantly when the tumour gains access to the sinus <sup>10</sup>. Once in the sinus, these tumours are difficult to completely resect. </p><p>They may compress cranial nerves resulting in deficits, although this is uncommon, seen in only 1-14% of cases <sup>10</sup>. <a href="/articles/oculomotor-nerve">Oculomotor nerve (CN III)</a> is most commonly involved, followed by the <a href="/articles/abducens-nerve">abducens nerve (CN VI)</a> <sup>10</sup>. </p><p>Radiological and surgical invasion <a href="/cases/grading-of-cavernous-sinus-invasion-by-pitutary-macroadenoma">grading system</a> characterised by areas distinguished from each other by a medial, median and lateral intercarotid lines: medial, lateral and central tangent on the intra- and supra cavernous internal carotid arteries on coronal view <sup>11</sup>.</p><h4>Pathology</h4><p>Most macroadenomas are non-secretory (endocrinologically inactive). They are a type of benign epithelial tumour composed of adenohypophyseal cells</p><h4>Radiographic features</h4><p>Pituitary macroadenomas are by definition &gt;10 mm mass arising from the pituitary gland, and usually extending superiorly. Indentation at the <a href="/articles/diaphragma-sellae">diaphragma sellae</a> can give a <a href="/articles/snowman-sign-pituitary-macroadenoma-1">snowman</a> or figure eight configuration <sup>10</sup>. </p><h5>CT</h5><p>Non-contrast attenuation can vary depending on haemorrhagic, cystic and necrotic components. Adenomas which are solid, without haemorrhage, typically have attenuation similar to brain (30-40 HU) and demonstrates moderate contrast enhancement; less marked than one typically sees in meningiomas. Calcification is rare.</p><h5>MRI</h5><p>MRI is the preferred imaging modality, not only able to exquisitely delineate the mass, but also clearly visualise the optic chiasm, anterior cerebral vessels and cavernous sinuses. </p><p>Overall signal characteristics can significantly vary depending on tumour components such as haemorrhage, cystic transformation or necrosis.</p><ul>
  • +<p><strong>Pituitary macroadenomas </strong>are the most common <a href="/articles/pituitary-region-masses">suprasellar mass</a> in adults, and responsible for the majority of trans-sphenoidal hypophysectomies. They are defined as <a href="/articles/pituitary-adenoma">pituitary adenomas</a> greater than 10 mm in size and are approximately twice as common as <a href="/articles/pituitary-microadenoma">pituitary microadenomas</a>. </p><p>On imaging, they usually present as a solid tumour with attenuation similar to the brain (30-40 HU) and demonstrates moderate contrast enhancement. The same is observed on MRI, where they are isointense to the grey matter both on T1- and T2-weighted images. However, attenuation and signal characteristics can significantly vary depending on tumour components such as haemorrhage, cystic transformation or necrosis.</p><p>For a general discussion, including epidemiology, treatment, and prognosis, please refer to the article on <a href="/articles/pituitary-adenoma">pituitary adenomas</a>. </p><h4>Clinical presentation</h4><p>Patients typically present with symptoms of local mass effect on adjacent structures (especially <a href="/articles/optic-chiasm">optic chiasm</a>). Some may present hormonal imbalance, with symptoms of hypopituitarism (from compression) or secretion. Hormonal imbalance due to overproduction tends to present earlier and tumours are thus usually small at presentation. This mode of presentation is discussed in the article on <a href="/articles/pituitary-microadenoma">pituitary microadenomas</a>. </p><p>Rarely <a href="/articles/pituitary-apoplexy">pituitary apoplexy</a> may present acutely and often catastrophically. </p><h5>Optic chiasm compression</h5><p>The <a href="/articles/supraoptic-recess-2">optic chiasm</a> is located directly over the pituitary gland in 80% of individuals. The rest are divided between pre and postfixed chiasms. A prefixed optic chiasm is located anterior to its normal position over the <a href="/articles/tuberculum-sellae">tuberculum sellae</a>, whereas a postfixed chiasm is located over the <a href="/articles/dorsum-sellae">dorsum sellae</a> <sup>10</sup>. </p><p>A macroadenoma growing superiorly out of the pituitary fossa (or for that matter other pituitary region masses) will contact, elevate and compress the central part of the chiasm in most individuals. This central part carries fibres from the nasal retina, and thus results in the classical bitemporal hemianopia <sup>10</sup>. Patients typically complain of bumping into things or having car accidents, but as the macular fibres are often spared, they may not be aware of actual visual deficits. </p><p>In cases of prefixed or postfixed chiasms, or when the macroadenoma grows asymmetrically, then the <a href="/articles/optic-nerve">optic nerves</a> or <a href="/articles/optic-tract">optic tracts</a> can be compressed, resulting in a variety of visual deficits. </p><h5>Cavernous sinus invasion</h5><p>Some macroadenomas demonstrate invasive growth, and extension into the <a href="/articles/cavernous-sinus">cavernous sinuses</a> is characteristic. Prolactin-secreting tumours are most frequently responsible for cavernous sinus extension, and typically prolactin level increase significantly when the tumour gains access to the sinus <sup>10</sup>. Once in the sinus, these tumours are difficult to resect completely. </p><p>They may compress cranial nerves resulting in deficits, although this is uncommon, seen in only 1-14% of cases <sup>10</sup>. <a href="/articles/oculomotor-nerve">Oculomotor nerve (CN III)</a> is most commonly involved, followed by the <a href="/articles/abducens-nerve">abducens nerve (CN VI)</a> <sup>10</sup>. </p><p>Radiological and surgical invasion <a href="/cases/grading-of-cavernous-sinus-invasion-by-pitutary-macroadenoma">grading system</a> characterised by areas distinguished from each other by a medial, median and lateral intercarotid lines: medial, lateral and central tangent on the intra- and supra cavernous internal carotid arteries on coronal view <sup>11</sup>.</p><h4>Pathology</h4><p>Most macroadenomas are non-secretory (endocrinologically inactive). They are a type of benign epithelial tumour composed of adenohypophyseal cells</p><h4>Radiographic features</h4><p>Pituitary macroadenomas are by definition &gt;10 mm mass arising from the pituitary gland, and usually extending superiorly. Indentation at the <a href="/articles/diaphragma-sellae">diaphragma sellae</a> can give a <a href="/articles/snowman-sign-pituitary-macroadenoma-1">snowman</a> or figure eight configuration <sup>10</sup>. </p><h5>CT</h5><p>Non-contrast attenuation can vary depending on haemorrhagic, cystic and necrotic components. Adenomas which are solid, without haemorrhage, typically have attenuation similar to the brain (30-40 HU) and demonstrates moderate contrast enhancement; less marked than one typically sees in meningiomas. Calcification is rare.</p><h5>MRI</h5><p>MRI is the preferred imaging modality, not only able to delineate the mass exquisitely, but also clearly visualise the optic chiasm, anterior cerebral vessels and cavernous sinuses. </p><p>Overall signal characteristics can significantly vary depending on tumour components such as haemorrhage, cystic transformation or necrosis.</p><ul>
  • -<li>calcification is rare, but should be excluded by reviewing CT scans</li>
  • +<li>calcification is rare but should be excluded by reviewing CT scans</li>

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