pituitary pathology Flashcards
Function of T-pit
Trxn factor which promotes differentiation of rathe pouch stem cells into corticotrophs which will secrete ACTH. Also involved in ACTH secreting pituitary adenoma.
Function of Pit-1
Trxn factor which promotes differentiation of Rathke pouch stem cells into somatotroph stem cells. Can also be involved in mixed GH/TSH secreting adenomas
What do somatotroph stem cells differentiate into
- Somatotrophs (secrete GH). 2. Thyrotrophs (secrete TSH)- can also convert back into somatotroph stem cells. 3. mammosomatotroph- further differentiates into somatotroph (GH) or latotroph (PRL)
distribution of cell types in anterior pituitary
Corticotrophs (ACTH) and thyrotrophs (TSH) in middle. Lactotrophs (PRL) and somatotrophs (GH) towards the sides
Staining of somatotrophs
Acidophilic (orangish) on PAS-orange G staining
normal anterior vs posterior pituitary histology
anterior: glandular with acidophilic, basophilic and chromophobic staining cells. Posterior: eosinophilic, fibrillar appearance with occasional swollen axonal processes (herring bodies)
Infundibulum histology
Congested, thin walled closely juxtaposed hypothalamic-hypophyseal portal system
Causes of pituitary adenomas
<5% are familial, the rest are sporadic with an unknown cause.
Genes associated with familial pituitary tumor syndromes
MEN1, CDKN1B, PRKAR1A and AIP (GH secreting adenomas)
Features suggesting an inherited pituitary tumor syndrome
parathyroid tumors, pancreatic endocrine tumors, atrial myxomas, lentigines, Schwann-cell tumors (Carney complex), family history and young age at onset
Pituitary tumor clinical presentation
- hormone hypersecretion: acromegaly, Cushings, amenorrhea/galactorrhea. 2. Sx from mass effect: headaches, vision loss, piuitary gland dysfunction
pituitary adenoma grade
Almost all are WHO grade 1
Microadenoma vs macroadenoma of anterior pituitary
Micro: 10mm, distorts adjacent tissues such as the dura of the sellar floor or diaphragma sella causing headaches
pituitary adenomas and diabetes insipidus
DI is quite uncommon with pituitary adenomas of any size
Macroadenomas most common growth patterns
Most commonly grows directly upwards, compressing the optic chiasm and resulting in bitemporal hemianopsia (loss of lateral visual fields due to compression of medial retinal fields).
Less common growth patterns of macroadenomas of pituitary
- compression of hypothalamus- hypothalamic dysfunction is rare. 2. Lateral growth outside the sella may compress the medial temporal lobe causing seizures. 3. May compress brain parenchyma but lack ability to infiltrate into brain parenchyma as single cells. 4. May extend laterally and compress the wall of the cavernous sinus, enwrapping the carotid artery (but not compromising) and distorting cranial nerves III, IV, and VI (cranial nerve palsies). 5. May extend into sphenoid sinus
Giant adenomas
Invasive adenomas >4cm
Imaging of macroadenomas and giant adenomas
Often show cysts and hemosiderin pigment in neuroimaging or in tumor specimen
Which pituitary tumors are responsive to medical therapy
Prolactinomas and GH secreting tumors (after surgical debulking)
Piuitary adenoma histology
intraoperative touch preparation shows abundant exfoliation of cytologically monotonous cells. Nuclear pleomorphism is uncommon. Mitoses are rare in microadenomas but occasionally seen in macro.
Histochemical stain for adenomas
Reticulin- normal pituitary has a nested pattern whereas adenoma has a disrupted reticulin pattern
Most frequency pituitary adenomas found incidentally at autopsy
prolactinoma, followed by null cell/gonadotroph
clinical signs of prolactinoma
galactorrhea, amenorrhea, infertility, hypogonadism
prolactinoma histology and immunoreactivity
Diffuse growth pattern, monotonous cell population with increased nuclear chromatin content and conspicuous vasculature. Diffuse immunoreactivity for PRL only.