Week 4: Pathology of the pituitary

Question 1

Anatomy of the pituitary gland

Answer 1

1. Anterior lobe
   - origin from Rathke pouch, arises from roof of primitive oral cavity
   - blood supply from venous portal system
   - vulnerable to hypoperfusion
2. Posterior lobe
   - from diencephalon, connected to brain via infundibular stalk
   - arterial blood supply

Question 2

Congenital abnormalities of pituitary gland

Answer 2

1. Aplasia: defective Rathke pouch formation
   - posterior lobe present, but anterior lobe absent. End organ hypoplasia
2. Anencephaly
   - absent posterior lobe
   - not compatible with life
3. Pharyngeal pituitary (congeintal rests)
   - small rest located in midline of nasopharynx, remnant of wrath pouch

Question 3

Vascular disturbances of the pituitary

Answer 3

1. pituitary apoplexy
   - sudden hemorrhage followed by necrosis in a pituitary enlarged by disease
   - usually underlying disease is macro adenoma (>10mm)
   - hemorrhage causes compression atrophy
2. Sheehan syndrome
   - infarction of hyper plastic anterior pituitary during hypovolemic shock due to bleeding in delivery
   - hypopituitarism occurs when there is 75-90% destruction

Question 4

Inflammation of pituitary gladn

Answer 4

1. Granulomatous: from TB, sarcoidosis, syphilis, mycoses
2. lymphocytic hypophysitis
   - more common in women
   - pregnancy or post partum
   - infiltration of anterior lobe by lymphocytes and plasma cells, with destruction and fibrosis. Can involve posterior pituitary
   - polyglandular autoimmune syndrome: involvement of thyroid, adrenals, parathyroid, pancreas

Question 5

Symptoms of pituitary neoplasms

Answer 5

1. Space occupying
   - bitemporal hemianopsia from pressing against optic chasm
   - increase intracranial pressure: nausea, vomiting, headache,
   - enlargment of sella turcica
   - nerve palsies if disruption of cavernous sinus
2. hormonal effects
   - increased trophic hormones
   - decreased trophic hormones from compression, hemorrhage, iatrogenic
   - stalk effect

Question 6

Pathology of Pituitary adenomas

Answer 6

• 10% of intracranial tumors
• microadenomas are less than 10mm
• most common: null cell adenoma, clinically silent until has mass effect
• second most common: prolactinoma, mainly macro adenomas (most common functioning adenoma)

Question 7

Cushing’s disease-pituitary pathology

Answer 7

• mostly caused by micro adenomas
• Nelson syndrome: rapidly enlarging pituitary tumor and skin hyper pigmentation occurring in Cushing’s disease patients previously treated with bilateral adrenalectomy
• Crooke’s hyaline change: corticotroph cells surrounding adenoma with circle of hyaline due to keratin filaments

Question 8

Pituitary involvement in MEN

Answer 8

MEN Type 1

• pituitary adenoma or hyperplasia
• pancreatic islet cell tumors
• parathyroid disease
• from chromosome 11q3 mutation

Question 9

Malignant pituitary neoplasms

Answer 9

• very rare
• mostly nonfunctional
• invasive
• highly mitotic

Question 10

Craniopharyngioma

Answer 10

• benign suprasellar mass originating from Rathke pouch
• in young individuals and also 60+ year olds
• space occupying lesion
• has areas of calcification
• microscopic: shows squamous epithelium, cysts, calcification
• cystic craniopharyngiomas: has thick, viscous fluid like motor oil and can have cholesterol crystals

Question 11

Pathology of pituitary syndromes

Answer 11

1. Diabetes insipidus- decreased ADH. Polyuria and polydipsia, low urine osmolality
2. SIADH
   - increased ADH, from CHS trauma, pituitary dysfunction, inflammations, lung disease
3. Metastatic carcinoma
   - breast, lung, thyroid and prostate are most common primary sites
4. Langerhans cell histiocytosis
   - granulomatous destructive lesions
   - Hand Schuller Christian disease: bony lesions, exophalmos, diabetes insipidus
   - CD1a and S100 positive
   - birbeck granules: rackets

Question 12

Empty Sella Syndrome

Answer 12

1. Primary: compression atrophy of pituitary due to arachnoid herniation containing CSF through a defect in diaphragma sella
2. secondary: due to spontaneous necrosis or surgical removal of pituitary adenoma