Pituitary adenomas may be classified based on their appearance in imaging studies. These were initially developed using skull radiographs but have been enhanced with CT and MRI scans.
Classification of adenomas is based on:
(1) enclosed vs invasive
(2) Grade
(3) suprasellar expansion/extension
Enclosed vs invasive (after Guiot et al):
(1) enclosed: the adenoma remains within the anatomical confines of the osteoaponeural sheath of the sella turcica. The floor of the sella is intact.
(2) invasive: The adenoma destroys the floor of the sella and herniates into the underlying sphenoidal sinus.
|
Growth |
Appearance on Imaging Studies |
Grade |
|
enclosed |
The sella turcica is within normal limit for size (< 16 x 13 mm, or 208 square mm), but shows a lowering of the floor on one side or bulging of the cortex. The floor remains intact. |
I |
|
enclosed |
The sella turcica is enlarged to various degrees but the floor remains intact. |
II |
|
invasive |
The sella is more or less enlarged but there is local erosion or destruction of the floor. |
III |
|
invasive |
The floor of the sella is diffusely eroded or destroyed giving a "phantom sella" where all of the boundaries are barely visible. |
IV |
A microadenoma is a Grade I tumor measuring < 10 mm in diameter.
|
Suprasellar extension (SSE) on X-ray |
Height above Jugum Sphenoidale on CT Scan |
Type |
|
extension bulges into the chiasmatic cistern but does not reach the floor of the anterior third ventricle |
1 – 10 mm |
A |
|
tumor reaches the floor of the third ventricle giving the image of an inverted cupula of the anterior recesses of the third ventricle |
11 – 20 mm |
B |
|
voluminous suprasellar expansion bulges largely into the third ventricle up to the foramen of Monroe |
21 – 30 mm |
C |
|
expands into temporal or frontal fossa |
31 – 40 mm |
D |
where:
• Typing was based on X-ray appearance (left column) prior to the ability to measure the extension more accurately using CT images (middle column).
• Mohr et al consider Type C or D as "giant" adenomas.
• I am not sure if there have been any showing an extension > 40 mm.
Specialty: Hematology Oncology, Surgery, general, Endocrinology, Neurology
