Primary Tumors of the Pituitary Gland: Radiologic–Pathologic Correlation

A practical radiology review of Primary Tumors of the Pituitary Gland: Radiologic–Pathologic Correlation, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

• Epidemiology & Basics

2. nd most common CNS tumor (after meningioma)

Most frequent in adolescents/young adults

Derived from 3 embryologic origins

• Adenohypophysis (anterior) → adenomas
• Rathke pouch → craniopharyngiomas
• Neurohypophysis (posterior) → pituicytoma spectrum

Adenohypophyseal Tumors

• Pituitary adenomas = 90–95% of cases
• Micro <10 mm | Macro ≥10 mm | Giant ≥40 mm
• MRI: delayed enhancement vs normal gland
• Dynamic post-contrast helps microadenoma detection
• Functional Types
• Lactotroph (Prolactinoma) → galactorrhea, amenorrhea; ↑PRL; dopamine agonists (cabergoline) effective
• Somatotroph (GH) → acromegaly/gigantism; T2 ↓ = densely granulated (better Rx response)
• Corticotroph (ACTH) → Cushing disease; “small tumor, big Cushing”
• Thyrotroph (TSH) → thyrotoxicosis; usually macroadenoma
• Gonadotroph → often silent, nonfunctional

Special Forms

• Silent adenomas: histologic activity but no hormone symptoms
• Null cell adenoma: hormone-immunonegative
• Plurihormonal / Double adenoma: multiple hormones or coexisting types
• Aggressive/invasive: cavernous sinus or bone invasion, rapid recurrence

Malignant & Rare

• Pituitary carcinoma: metastases (CNS/systemic), poor prognosis
• Pituitary blastoma: infants <2y with Cushing; DICER1 mutation

Rathke Pouch Lesions

• Rathke cleft cyst (RCC) nonneoplastic, thin wall, T1/T2 variable, no solid enhancement

Craniopharyngioma

• Adamantinomatous (ACP): children/bimodal; cystic + calcified; β-catenin mutation
• Papillary (PCP): adults; solid; BRAF V600E mutation

Neurohypophyseal Tumors (TTF-1⁺)

• Pituicytoma, Granular cell tumor, Spindle cell oncocytoma → solid enhancing masses in infundibulum/posterior pituitary

Imaging Pearls

• MRI = modality of choice
• Microadenoma → dynamic post-contrast
• Macroadenoma → suprasellar extension, infundibular displacement
• Knosp grade (ICA encasement) for invasiveness
• CT: sella erosion, calcifications (ACP)
• T2 FLAIR: helps detect delayed washout (microadenoma)

Key Takeaways

• Match tumor type → cell origin → hormone → imaging pattern
• Recognize ACP vs PCP, adenoma vs RCC, adenoma vs pituicytoma
• Confirm with IHC (Pit-1, ACTH, TTF-1, β-catenin, BRAF VE1)
• Always correlate clinical + hormonal + MRI + histopathology for diagnosis