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.

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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)

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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.

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