Evaluation of Sellar Mass
When a sellar mass is discovered, immediately consult an endocrinologist for comprehensive hormonal evaluation and detailed MRI imaging, with neurosurgical consultation added for lesions ≥10 mm, those with cavernous sinus invasion, visual symptoms, or proximity to the optic chiasm 1.
Initial Diagnostic Workup
Imaging Protocol
- MRI with contrast is the imaging modality of choice for characterizing sellar masses 1, 2
- Obtain dedicated pituitary protocol MRI including:
- T1-weighted sequences (pre- and post-contrast)
- T2-weighted sequences
- Coronal and sagittal views
- Assessment of optic chiasm proximity and cavernous sinus invasion
Hormonal Evaluation
Perform comprehensive endocrine testing for both hypersecretion and hyposecretion 1, 3:
Hypersecretion screening:
- Prolactin level (hyperprolactinemia)
- IGF-1 (acromegaly)
- 24-hour urinary free cortisol or late-night salivary cortisol (Cushing's disease)
- Consider ACTH if Cushing's suspected
Hyposecretion assessment:
- Morning cortisol and ACTH
- TSH and free T4
- LH, FSH, testosterone (men) or estradiol (women)
- For suspected diabetes insipidus: urine osmolality and 24-hour fluid intake/output record 3
Ophthalmologic Assessment
- Formal visual field testing is mandatory for any macroadenoma (≥10 mm) or lesion with suprasellar extension 1
- Particularly critical when lesion abuts or approaches the optic chiasm
Key Diagnostic Considerations
Distinguishing Features by Lesion Type
Pituitary adenomas (most common):
- Solid appearance on MRI
- Homogeneous or heterogeneous enhancement
- More likely to enlarge than cystic lesions 1
- Macroadenomas grow at 10-14 events per 100 person-years vs. 2-5 for microadenomas 1
Rathke cleft cysts (13-17% of incidentalomas) 3:
- Often contain waxy nodule
- ~40% hypointense on T2, hyperintense on T1
- Minimal enhancement with thin wall
- Located in pars intermedia with anterior stalk displacement 1
- Can present with diabetes insipidus (4.6% of cases) 3
Craniopharyngiomas:
- Often calcified
- Cystic and solid components
- Suprasellar location common
Critical Pitfalls to Avoid
Do not assume all sellar masses are pituitary adenomas - 20-26% are non-adenomatous lesions including Rathke cleft cysts, craniopharyngiomas, and rarely other pathologies 1, 4
Hypervascular, firm tumors at surgery suggest alternative diagnoses (e.g., solitary fibrous tumor, meningioma) even when imaging suggested adenoma 4
Partial diabetes insipidus can be unmasked by glucocorticoid replacement - monitor for polyuria after starting hydrocortisone 3
Indications for Urgent Specialist Referral
Refer immediately to endocrinology AND neurosurgery for 1:
- Adenoma ≥10 mm or cavernous sinus invasion
- 15-20% growth in maximum diameter on serial imaging
- Visual field deficits or lesion abutting/near optic chiasm
- Ophthalmoplegia or severe headaches
- Clinical signs of hypopituitarism or hormone hypersecretion
- Pregnancy or desire for pregnancy
Surveillance Strategy After Initial Evaluation
For Microadenomas (<10 mm):
- First repeat MRI at 2-3 years unless near optic chiasm 1
- For stable microadenomas <5 mm: consider discontinuing surveillance after one stable repeat MRI 1
- For microadenomas ≥5 mm: continue surveillance every 2-3 years if stable
For Macroadenomas (≥10 mm):
- First repeat MRI at 6 months if <5 mm from optic chiasm 1
- First repeat MRI at 6-12 months if ≥5 mm from optic chiasm 1
- Subsequently:
For Rathke Cleft Cysts:
- Asymptomatic small RCCs (<10 mm): serial MRI at 1,3, and 5 years if stable 3
- Surgery indicated for: enlarging lesions, visual dysfunction, hormonal dysfunction, or intractable headache 1, 3
High-Risk Features Predicting Clinical Significance
Macroadenomas are at substantially higher risk than microadenomas for 1:
- Growth (34% vs. 12%)
- Apoplexy (5% vs. <1%)
- Visual deficits (fourfold increased risk)
- Hypopituitarism (threefold increased risk)
Growth rate >5.9 mm/year or increase >3.5 mm overall predicts visual deterioration 1, warranting surgical consideration.