166. Hypothalamus-Pituitary Histology/Pathology Flashcards
Lying at interface b/w adeno- and neurohypophysis
Cystic change is frequent
Likely the site of origin of Rathke’s cleft cysts
Pars intermedia
Second most common adenoma found
Most are macroadenomas 2 types: - sparsely granulated (~10%) - look for fibrous bodies —> more aggressive
- Densely granulated (~10%) Prolactin reactivity often present in addition to GH Elevated IGF-1 => gigantism and acromegaly
GH-producing (somatotroph cell) adenomas
Often associated w/ systemic sarcoidosis
Preferentially affects structures in the suprasellar region
Produces non-caseating, granulomatous inflammation with multinucleated (Langhans’) giant cells
CNS sarcoidosis
Most often in adults
Papillae line by well-differentiated squamous epithelium
Lack keratin, peripheral palisading, calcification, and cysts
Good prognosis
Papillary craniopharyngioma
Craniopharyngiomas
Germ cell tumors
Hypothalamic suprasellar tumors
Most common variant of pituitary adenoma
Microadenomas or macroadenomas
Amenorrhea/galactorrhea in females; impotence, loss of libido in males
Usually diagnosed earlier in women of reproductive age than in postmenopausal women and in males
Majority are responsive to bromocriptine and relate drugs (cabergoline)
Prolactin-producing adenomas
Hypercorticolism due to ACTH adenoma
Cushing’s Disease
On histology: - Sparsely granulated (~20-30%) - Densely granulated (~1%) - Dystrophic calcification = pituitary stone
Prolactinoma
Most commonly seen in children
Consists of stratified squamous epithelium w/ periphery palisading and compact, lamellar keratin formation = wet keratin
Dystrophic calcification Cysts of the tumor contain “machine oil” Good prognosis
Adamantinomatous craniopharyngioma
Derived from Rathke’s pouch
Bimodal age distribution:
- 5-15yo
- 65yo and up
Manifestation:
- headaches
- visual disturbances
- growth retardation d/t GH deficiency
Craniopharyngiomas
25-30% of pituitary adenomas
Macroadenomas Symptoms d/t mass effect and/or hypopituitarism
Synaptophysin and chromogranin reactive; otherwise minimally or nonreactive - nonfunctioning
Null cell adenomas or silent variants
Originate from remnants of the Rathke’s pouch
Simple cyst composed of ciliated cuboidal epithelium
Rathke’s cleft cyst
Most common tumors of the anterior pituitary
Most common cause of hyperpituitarism
Manifestations related to:
- Secretion of excess hormone
- Hypopituitarism
- Mass effect
Pituitary adenomas
Specialized glial cells that support the axons in the posterior lobe of the pituitary gland
Pituicytes
On histology:
- Populated by epithelial cells containing a variety of trophic hormones
- Cells compartmentalized into small acini by a reticulin network
Anterior pituitary
Results in hyponatremia
Caused by both extra-CNS disorders (most common) and some CNS diseases Extra-CNS causes include neoplasia (small cell carcinoma of the lung), adrenal insufficiency, myxedema, cirrhosis, cardiac disease, certain drugs CNS causes include trauma, CNS infections, CNS neoplasms, etc. - anything w/ blood volume loss really
SIADH (Inappropriate ADH secretion)
Diseases referable to abnormalities in ADH release
- no well-defined syndromes related to oxytocin abnormalities Diabetes insipidus and SIADH
Posterior pituitary syndromes
Supplied by an artery and drains into a vein
- inferior hypophyseal branches Its hormones are released directly into the systemic circulation
Posterior lobe of pituitary gland
Elevated prolactin levels due to tumor secretion must be distinguished from… Levels < 150 ng/mL may represent this
Stalk Effect
2 hormones secreted by supraoptic and paraventricular nuclei of hypothalamic innervation to the posterior pituitary
Oxytocin and vasopressin (ADH)
Most common CNS germ cell tumor
Children and young adults
Usually in the pineal or suprasellar region
Lymphocytic infiltration seen everywhere on slides
Germinoma
Defined by the presence of metastasis and/or craniospinal dissemination
Poor correlation with cytological atypia
Most are hormonally active
Extremely rare - clinical diagnosis bc tumor looks like regular adenoma on slides
Pituitary carcinoma
Blood supply of the anterior pituitary
Conduit for the transport of hypothalamic releasing hormones from the hypothalamus
Hypophyseal portal system
Enlargement of ACTH adenoma after the removal of both adrenal glands
Nelson Syndrome
Connects the hypothalamus to the pituitary gland
Pituitary stalk
Most common during pregnancy or postpartum period - autoimmune disorder
- both cellular and humoral responses in pathogenesis
Symmetrical enlargement of pituitary accompanied by pituitary insufficiency
May occur in isolation or in conjunction with autoimmune infiltrates in other endocrine organs
Destructed gland seen on histology
Lymphocytic hypophysitis
Pathogenesis of pituitary adenomas is fairly uncertain in most cases except for the cases in patients with this condition
MEN-1
Derived from Rathke pouch
From oral ectoderm
Anterior pituitary (adenohypophysis)
General morphological features:
- Cytoplasm of constituent cells tends to be monomorphous compared to non-neoplastic gland
- Paucity of reticulin network
- Low mitotic activity
- Atypical categorization –> ki-67 labeling index > 3% w/ p53 expression
Pituitary adenomas
Acidophilic cells of the 5 cell types in anterior lobe of pituitary gland
GH- and prl-secreting cells
Represents a downward (ventral) outgrowth of the embryonic diencephalon
- ventral outgrowth of the hypothalamic floor
From neuronal ectoderm
Posterior pituitary
Usually microadenomas at the time of diagnosis
Basophilic, densely granulated, strongly PAS, and ACTH-reactive
Associated w/ hypercorticolism
- Cushing syndrome
- Cushing disease
- Nelson syndrome
ACTH-producing adenomas
Populated by axons originating in neurons in the supraoptic and paraventricular nuclei of the hypothalamus
- secrete oxytocin and vasopressin (ADH)
Posterior lobe (neurohypophysis)
Cell populations: acidophil (w/ eosinophilic cytoplasm), basophil (w/ basophilic cytoplasm), and chromophobe (poorly staining cytoplasm)
Five cell types:
- Somatotrophic - GH
- Lactotrophic - prolactin, prl
- Corticotrophic - ACTH
- Thyrotrophic - TSH
- Gonadotrophic (FSH, LH)
Anterior lobe (adenohypophysis)
Hypercorticolism regardless of cause
Cushing syndrome
Confines the pituitary gland
Sella turcica and sellar diaphragm
In conjunction with the hypothalamus, plays a central role in modulating the exocrine system
Lies in close proximity to the hypothalamus
Pituitary gland
Extra-CNS cause of SIADH that is quite common
- cancer
Small cell carcinoma of lung
Extension of the developing oral cavity Gives rise to anterior lobe
Rathke pouch
Excessive urination (polyuria)
Can be subdivided into central and nephrogenic variants
Central variants include primary = idiopathic or hereditary, trauma, vascular disease, suprasellar/hypothalamic neoplasms, local infections, inflammatory diseases
Diabetes insipidus
Axonal expansions found on histology as finely granular round structures that contain ADH and oxytocin
Herring bodies
Delicate collagen fibers that hold the anterior lobe together
Reticulin network
Elevated IGF-1 from GH-producing adenomas leads to…
Gigantism - children Acromegaly - adults
Low pressure blood supply renders this area vulnerable to ischemic insults d/t things like hypotension and elevated ICP
Anterior pituitary
