What is the management approach for a patient with a sellar mass on MRI?

Management of a Sellar Mass on MRI

Obtain comprehensive hormonal screening and ophthalmologic evaluation immediately, followed by high-resolution MRI with and without contrast if not already performed, to guide definitive treatment planning. 1, 2

Initial Diagnostic Workup

Hormonal Assessment

• Perform comprehensive endocrine testing including: 2

  • Thyroid function tests (TSH, free T4)
  • Morning cortisol and ACTH
  • Prolactin level (critical for distinguishing prolactinoma from stalk compression)
  • Sex hormones (LH, FSH, testosterone/estradiol)
  • Growth hormone/IGF-1

• Prolactin interpretation is crucial for treatment decisions: A prolactin >200 ng/mL strongly suggests prolactinoma, while levels 25-125 ng/mL require careful analysis combining tumor size and prolactin level to distinguish true prolactinoma from stalk effect. 3

Ophthalmologic Evaluation

• Obtain formal visual field testing and visual acuity measurement, particularly for macroadenomas (>10 mm), as visual recovery is unlikely after the first postoperative month and delays worsen outcomes. 2

Imaging Optimization

• If the initial MRI was not a dedicated pituitary protocol, obtain high-resolution MRI of the sella with and without IV contrast using thin-section imaging (≤0.5 cm slice thickness) with pre- and post-contrast T1-weighted sequences. 1, 2

• MRI is superior to CT for characterizing sellar masses, providing detailed visualization of the pituitary gland, infundibulum, optic chiasm, and cavernous sinus invasion. 1

Differential Diagnosis Considerations

Common Lesions

• Pituitary adenomas account for the majority of sellar masses (approximately 82% of visible lesions), with prolactinomas (40%), nonfunctioning adenomas (37%), and GH-secreting adenomas (13%) being most common. 4

• Nonadenomatous lesions comprise 18% of sellar masses, including Rathke's cleft cyst (19%), craniopharyngioma (15%), and meningioma (15%). 4

Key Distinguishing Features

• Meningiomas show homogeneous enhancement with a "dural tail" sign in one-third of cases, have a 6:1 female predominance, and may cause mild hyperprolactinemia (mean 51.6 ng/mL) due to stalk compression. 5

• Metastases account for 5% of nonpituitary sellar lesions, with breast cancer being the most common primary source. 4

Treatment Algorithm

For Prolactinomas

• Initiate dopamine agonist therapy (cabergoline or bromocriptine) as first-line treatment when prolactin >200 ng/mL or when prolactin 40-125 ng/mL with tumor size <25 mm. 3

For Non-Prolactinoma Lesions

• Transsphenoidal resection is the mainstay of treatment for most sellar tumors except prolactinomas, with complete resection being the treatment of choice when feasible. 2

• Avoid attempting complete resection of tumors enveloping major vessels or involving vital neural structures, as risks outweigh benefits. 2

For Cystic Lesions (Type C on MRI)

• Conservative follow-up is justified for cystic lesions with smooth, thin walls in asymptomatic or transiently symptomatic patients, as these frequently shrink or disappear spontaneously. 6

For Solid Lesions >14 mm (Type S on MRI)

• Closer observation or treatment is warranted, as these often enlarge and become symptomatic over time (6 of 9 patients in one series required treatment). 6

Specialized Testing Scenarios

When Cushing Disease is Suspected

• Perform bilateral inferior petrosal sinus sampling (BIPSS) when pituitary lesions <6 mm are detected, MRI is negative/equivocal, or there is discordance between biochemical testing and imaging. 7

When Imaging is Negative but Hormonal Excess Persists

• Venous sampling of the cavernous sinuses is reserved for cases with definite pituitary hormone excess, failed medical management, and negative/equivocal imaging when surgery is planned. 1

Critical Pitfalls to Avoid

• Do not attribute all hyperprolactinemia to prolactinoma: Stalk compression from any sellar mass can elevate prolactin. Use the algorithm: prolactin >41.5 ng/mL, age <40.5 years, and size <17 mm predict prolactinoma with 92.1% accuracy. 3

• Do not delay surgical planning for resectable non-prolactinoma lesions causing visual symptoms, as visual recovery becomes unlikely after one month postoperatively. 2

• Do not overlook the need for lifelong endocrine surveillance, as hormonal deficiencies may develop or progress over time even after successful treatment. 2

• Do not assume normal pituitary function without testing: Approximately 30% of patients with empty sella demonstrate hypopituitarism, and 47% of pituitary MRI scans in one large series showed no visible lesion despite clinical suspicion. 8, 4

Postoperative Management

• Obtain histopathological assessment including immunostaining for pituitary hormones and Ki-67, as Ki-67 ≥3% combined with local invasion predicts 25% recurrence rate in pediatric cases. 2

• Perform delayed surveillance imaging >3 months following transsphenoidal surgery for known subtotal resection or nonfunctioning adenomas, guided by tumor pathology and patient symptoms. 1