Sellar space-occupying lesions refer to abnormal tissues or masses arising within the sellar region of the skull base. Such lesions may compress vital adjacent structures including the pituitary gland, optic nerves and hypothalamus, triggering clinical manifestations such as headache, visual impairment and endocrine dysfunction. The etiologies of sellar masses are highly heterogeneous, covering neoplastic lesions, inflammatory disorders, vascular anomalies and other pathological conditions. This article systematically elaborates on common causes, pathological mechanisms, clinical manifestations and core diagnosis & treatment principles of sellar space-occupying lesions.

I. Pituitary-Related Lesions: The Most Prevalent Cause

1. Pituitary Adenomas

Pituitary adenomas constitute the most common sellar space-occupying lesions, accounting for 60%–70% of all sellar masses. They are classified into functional adenomas (prolactinomas, growth hormone-secreting adenomas, etc.) and non-functional adenomas based on autonomous hormone secretion.

• Pathological mechanism: Abnormal proliferation of adenoma cells compresses normal pituitary parenchyma and disrupts physiological hormone balance. Prolactinomas induce amenorrhea-galactorrhea in females and sexual dysfunction in males; growth hormone adenomas lead to acromegaly in adults or gigantism in children and adolescents.

• Imaging features: MRI reveals round or oval intrasellar/suprasellar masses with homogeneous or heterogeneous contrast enhancement. Macroadenomas may herniate through the diaphragma sellae and compress the optic chiasm, resulting in bitemporal hemianopia.

• Treatment: Surgical resection via the endonasal transsphenoidal approach serves as first-line therapy; postoperative medical management (e.g., bromocriptine) or radiotherapy is applied to normalize hormone levels for residual disease.

2. Hypophysitis

Hypophysitis is a rare inflammatory sellar disorder, categorized into lymphocytic hypophysitis, granulomatous hypophysitis and other subtypes.

• Etiology: Autoimmune responses (e.g., postpartum lymphocytic hypophysitis), infectious pathogens (tuberculosis, syphilis) or adverse reactions to pharmaceutical agents (immune checkpoint inhibitors).

• Clinical manifestations: Headache, visual deficits and hypopituitarism including adrenal insufficiency and hypothyroidism. Some patients develop pituitary apoplexy, presenting with sudden severe headache and altered consciousness.

• Diagnosis: MRI demonstrates diffuse pituitary enlargement with low T1 signal and homogeneous contrast enhancement, distinguishable from nodular enhancing pituitary adenomas.

II. Congenital and Developmental Abnormalities: Lesions Derived from Embryonic Remnants

1. Craniopharyngioma

Craniopharyngiomas originate from residual epithelial cells of the embryonic craniopharyngeal duct, accounting for 5%–10% of sellar tumors.

• Pathological features: Mostly cystic or cystic-solid lesions containing cholesterol crystals within cyst fluid; calcification is readily visible on CT scans.

• Clinical manifestations: Pediatric patients primarily present with growth retardation and diabetes insipidus; adult patients develop visual impairment and hypopituitarism. Mass compression of the third ventricle may trigger obstructive hydrocephalus.

• Treatment: Radical surgical resection is technically challenging with high recurrence risk, requiring adjuvant radiotherapy postoperatively. Lifelong hormone replacement therapy is necessary for most patients.

2. Rathke's Cleft Cyst

Rathke's cleft cysts arise from congenital developmental defects of Rathke's pouch, filled with clear or turbid cystic fluid.

• Clinical symptoms: The majority of lesions remain asymptomatic; symptomatic patients experience headache, visual dysfunction and endocrine disturbances such as menstrual disorders and galactorrhea.

• Imaging manifestations: MRI shows round intrasellar/suprasellar lesions with high signal on both T1 and T2 weighted sequences and no contrast enhancement.

• Treatment: Asymptomatic cysts are managed with regular surveillance; surgical resection yields excellent prognosis for symptomatic lesions.

III. Neoplastic Lesions: Benign and Malignant Tumors

1. Meningioma

Meningiomas derive from arachnoid cap cells, making up 10%–15% of sellar tumors.

• Pathological features: Predominantly benign, slow-growing masses that compress the optic nerves and cavernous sinus.

• Clinical manifestations: Decreased visual acuity, peripheral visual field defects and extraocular movement disorders; partial patients develop hypopituitarism.

• Imaging features: MRI displays iso-intense masses at the tuberculum sellae or parasellar region with intense homogeneous enhancement and characteristic dural tail sign.

2. Metastatic Tumors

Sellar metastases are relatively uncommon, with primary malignancies mainly including breast cancer, lung cancer and prostate cancer.

• Metastatic pathways: Hematogenous dissemination, direct invasive spread or cerebrospinal fluid seeding.

• Clinical manifestations: Hypopituitarism (diabetes insipidus), headache and visual impairment; in rare cases, sellar metastasis represents the initial presentation of systemic malignancy.

• Treatment: Systemic therapy (chemotherapy, targeted therapy) forms the core management, supplemented by local radiotherapy to relieve compressive symptoms.

IV. Inflammatory and Infectious Lesions: Secondary Sellar Pathologies

1. Pituitary Abscess

Pituitary abscesses mostly stem from hematogenous infection or contiguous spread of adjacent infectious lesions such as sinusitis and meningitis.

• Core symptoms: High fever, severe headache, acute visual deterioration and complete pituitary failure.

• Imaging findings: MRI shows ring-enhancing intrasellar lesions with surrounding cerebral edema.

• Treatment: Emergency surgical drainage combined with long-course intravenous antibiotic therapy.

2. Neurosarcoidosis

Sarcoidosis is a systemic granulomatous disease capable of infiltrating the pituitary gland.

• Clinical manifestations: Hypopituitarism, diabetes insipidus and visual dysfunction.

• Diagnostic criteria: Combined evaluation of systemic manifestations (pulmonary nodules, cutaneous erythema) and histopathological biopsy results.

V. Vascular Lesions: Acute Life-Threatening Risks

1. Intracranial Aneurysm

Rupture of intracranial aneurysms causes subarachnoid hemorrhage and secondary sellar compression.

• Etiology: Congenital vascular wall defects (80%–90% of cases), atherosclerosis, infectious vasculitis or traumatic injury.

• Typical symptoms: Sudden explosive headache, nausea and vomiting, altered consciousness; oculomotor nerve palsy (ptosis, mydriasis) occurs in partial patients.

• Diagnosis: CTA or DSA precisely delineates aneurysm location and morphological characteristics.

2. Cavernous Sinus Thrombosis

Cavernous sinus thrombosis is induced by local infection or systemic hypercoagulable states.

• Clinical manifestations: Exophthalmos, eyelid swelling, decreased vision and ophthalmoplegia.

• Treatment: Antibiotics to control underlying infection and anticoagulant therapy to prevent thrombus extension.

VI. Traumatic and Iatrogenic Lesions

1. Pituitary Apoplexy

Pituitary apoplexy refers to intratumoral hemorrhage or infarction within a pre-existing pituitary adenoma, most frequently occurring in macroadenomas.

• Precipitating factors: Blood pressure fluctuations, anticoagulant medication and radiotherapy.

• Clinical manifestations: Sudden headache, acute vision loss, ophthalmoplegia and impaired consciousness.

• Treatment: Emergency surgical decompression combined with hormone replacement therapy.

2. Post-Sellar Surgery Changes

Scar tissue formation or empty sella syndrome may develop after pituitary adenoma resection or radiotherapy, leading to persistent hypopituitarism.

VII. Diagnosis and Differential Diagnosis

1. Imaging Examinations

• MRI: Gold standard examination to clearly visualize lesion location, size and anatomical relationships with surrounding structures. Pituitary adenomas present iso-intense or slightly hypointense signal with contrast enhancement; Rathke's cleft cysts show high signal on both T1 and T2 sequences.

• CT: Applied to screen intralesional calcification (craniopharyngioma) or acute hemorrhage (pituitary apoplexy).

2. Endocrine Laboratory Testing

• Baseline hormone assays: Abnormal levels of PRL, GH, ACTH and other pituitary hormones confirm functional adenomas.

• Dynamic endocrine tests: Dexamethasone suppression test differentiates pituitary-dependent and adrenal-dependent Cushing syndrome.

3. Histopathological Biopsy

Tissue samples are obtained via open surgery or transsphenoidal puncture to confirm pathological subtypes including metastatic tumors and lymphoma.

VIII. Treatment and Long-Term Management

1. Surgical Therapy

• Endonasal transsphenoidal approach: Minimally invasive resection for pituitary adenomas, Rathke's cleft cysts and other midline sellar lesions with minimal trauma and rapid postoperative recovery.

• Craniotomy: Reserved for complex lesions such as large craniopharyngiomas and invasive meningiomas.

2. Radiotherapy

• Conventional fractionated radiotherapy: Indicated for postoperative residual or recurrent tumors.

• Stereotactic radiosurgery (Gamma Knife): Delivers precise focal radiation to target tumor tissue.

3. Pharmacotherapy

• Dopamine agonists (bromocriptine): First-line medical control for prolactinomas.

• Somatostatin analogues (octreotide): Suppress excess GH secretion to alleviate acromegalic symptoms.

• Hormone replacement therapy: Supplement thyroid hormone, cortisol and sex hormones for patients with permanent hypopituitarism.

IX. Prevention and Clinical Recommendations

1. Regular physical examinations, especially for patients with a family history of pituitary adenomas or long-term radiation exposure.

2. Strict control of underlying chronic diseases; patients with hypertension or diabetes require regular endocrine function screening.

3. Avoid severe head trauma to reduce the risk of aneurysm rupture.

4. Standard postpartum follow-up for all women to screen for lymphocytic hypophysitis.

Summary

Sellar space-occupying lesions have complex and diverse etiologies covering neoplastic, inflammatory, vascular and traumatic pathologies. Early diagnosis relies on detailed medical history collection, systematic endocrine testing and high-resolution radiological assessment, while treatment plans must be individualized according to lesion pathological subtype. Genetic testing serves as an auxiliary screening tool for high-risk populations such as patients with familial pituitary adenoma syndromes. Multidisciplinary collaborative diagnosis and treatment enables favorable long-term prognosis for the majority of patients.