Pituitary Tumours

This is a normal anterior pituitary gland histology. Note the bluish colour of the basophils, and pinkish colour of the acidophils.

This is a histology slide of the posterior pituitary.

The brown-stained cells are cells that secrete Growth Hormones – Somatotropes. The cells are stained for immunochemistry evaluation.

_____________________________________________________________________

Pituitary Tumours

**Definition: Neoplasm located in the sella turcica.

Comprises of 10-15% of all intracranial tumours. 27% pituitary glands contain incidental adenomas (very common in people). 1/5 show pituitary abnormality on MRI. Uncommon in children, 2%.

Types of pituitary tumours:

1) Pituitary adenomas from adenohypophyseal – anterior pituitary (most)

2) Pituitary carcinoma (small percentage)

3) Mesenchymal, Neural, Epithelial, Metastases

Pituitary Adenoma

Most common:

1) Prolactinoma – in adults & children

2) ACTH-oma – more frequent in children

Signs & Symptoms – 2 concepts

1) Excessive hormone

• If it’s a funtioning tumour: high hormone level
• Non-functioning tumour: normal hormone level

2) Mass effect

• Intracranial mass: headache
• Loss of normal anterior pituitary hormone production due to compression
• Visual field defect: compression of optic chiasma (tunnel vision)
• Mild hyperprolactinemia (**stalk effect)

Classification

1) Functional – hormone level
2) Histology
3) Ultrastructural
4) Biochemical
5) Imaging
6) Surgical findings

Classification by size (imaging)

Microadenoma – <1cm
Macroadenoma – >1cm
Giant adenoma – >4cm (RARE)

Evaluate growth pattern, expansile, invasive.

Histology

• Monomorphic (just larger/more. No dysplasia)
• Uniform round cells
• Delicate stippled chromatin
• Inconspicuous nucleoli
• Moderate amounts of cytoplasm
• Mitoses: rare
• Ki67 labelling <3% (determine growth)
• Atypical variant

Treatment

1) Surgical – Via transphenoidal approach (minimally invasive)

Only perform surgery when:

• Progressive mass effect (visual loss)
• Hyperfunction (Cushings, acromegaly, hyperthyroid)
• Failure of medical treatment
• Massive acute haemorrhagic necrosis of an adenoma (pituitary apoplexy/Sheehan’s syndrome)

Sheehan’s syndrome – Haemorrhagic & infarcted

2) Medical treatment

Prolactinoma: Give dopamine agonist (inhibits prolactin). Reduces hyperprolactinemia, reduce tumour size.

GH-oma: Somatostatin analogues react with receptors, prevent growth hormone secretion. Does not reduce tumour size.

3) Radiation (Gamma Knife)

Use in:

• Incomplete surgical resection
• Recurrent tumors
• Medically unfit for surgery
• Secretory tumours uncontrolled by other treatment

Complication:

• hypopituitarism
• glioma (tumour of glial cells)
• sarcoma (malignant cancer of CT)

_____________________________________________________________________

Prolactinomas

*Most frequent type

• Cytoplasm weakly acidophilic
• Sparsely granulated/densely granulated
• Dystrophic calcification – pituitary stone

Characterised by: efficiency ( small tumours will also secrete hormone) and proportionality (hormone production proportional to tumour size)

Clinical features:

1) Amenorrhea
2) Galactorrhoea
3) Loss of libido
4) Infertility

These clinical features can also be caused by : prolactinemia, pregnancy, suckling and stress.

Prolactinaemia:

Due to hyperplasia of the lactotroph (secrete prolactin). It can be caused by:

1) Interference with dopamine inhibition (no inhibition of lactotroph)
2) Damage to dopanergic neurons of hypothalamus from trauma (no dopamine)
3) Mass in suprasellar compartment : Stalk effect

Growth Hormone Adenoma

**2nd most common

It will grow to be quite large before it will be clincally symptomatic. It is acidophilic (sparsely/densely granulated)

Immunohistochemistry: GH+ , CK+

Diagnosis:

• High level of growth hormone
• High level of IGF-1
• No suppression of GH with glucose loading

Corticotroph Adenoma

May be basophilic/ acidophilic.

• Usually small
• Most often densely granulated & basophilic
• PAS positive (bcos of carbohydrate content)

Immunohistochemistry: ACTH positive

Clinical features:

• Cushing’s syndrome (collection of signs & symptoms)
• Cushing’s disease (if pituitary tumour)
• Nelson syndrome
  -Largely destructive adenoma develop after surgical removal of adrenal glands
  -Hyperpigmentation (MSH)
  -Mass effect
  -No hypercortisolism

Nelson syndrome
Gonadotroph adenoma

-LH, FSH

Inefficient & variable secretion
No recognisable syndrome

Thyrotroph adenoma

Non-functioning adenomas
-silent

Pituitary Carcinoma

Must show METASTASES.

Suprasellar tumours

Effect: Induced hypo/hyperfunctioning of anterior pituitary / diabetes mellitus / both.

2 main types:

1. Gliomas from chiasma
2. Craniopharyngiomas (most)

Craniopharyngioma

It is an epithelial tumours (stratified squamous cell epithelia). It represents a bimodal distribution (5-15 years old & 50 years above). Histologically: 3-4cm, encapsulated, cystic/ solid.

2 variants:

1. Adamantinomatous
   
   Stratified squamous epithelium
   Loose reticulum
   Compact lamellar keratin (wet keratin)
   Ca
   lcification
   Chronic inflammation
   Cholesterol rich yellowish fluid – machinery oil fluid
2. Papillary

   Solid & papillary sheets of squamous epithelium
   No keratin
   No calcification
   No cysts
   No reticulum

Malignant transformation of craniopharyngiomas are RARE, unless there has been radiation.