Pituitary and Sellar tumors Flashcards
Papillary craniopharyngioma
Available WHO grades: 1
Morphology: Encapsulated tumor with well differentiated nonkeratinizing squamous epithelium and papillary fibrovascular stroma. Sometimes the fibrovascular stroma mixes with neuropil.
Thought to arise from Rathke cleft cysts.
Driven by BRAF V600E mutations
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Adamantinomatous Craniopharyngioma
Available WHO grades: 1
Morphology: Cords, lobules, nodular whorls and trabeculae of well differentiated squamous epithelium bordered by palisading columnar epithelium. Nodules of plump, anucleate squamous cells (ghost cells) and “wet keratin” are characteristic, and often have an associated xanthogranulomatous reaction. Piloid gliosis and Rosenthal fibers in may be seen in the adjacent brain.
The main diagnostic features (wet keratin and stellate reticulum) are shown.
Thought to arise from Rathke cleft cysts.
Driven by CTNNB1 mutations or other WNT pathway abnormalities (for example, aberrant SMAD3 methylation).
Rathke cleft cyst
Cyst which may contain mucin. May be intrasellar or suprasellar.
Classically has respiratory epithelium and occasional goblet cells, however may have squamous metaplasia. Some contain pieces of pituitary tissue.
Spindle cell oncocytoma
Available WHO grades: 1
Rare pituitary tumor arising from the adenohypophysis. It is a subtype of pituicytoma arising from oncocytic pituicytes.
Morphology: Spindled and polygonal cells arrange in fascicles. Chromatin is often condensed and there is moderate nuclear atypia. Like other oncocytic neoplasms, their granular eosinophilic cytoplasm comes from their numerous mitochondria.
Immunohistochemistry: TTF1+, S100 +, Galectin-3 +, EMA +, GFAP variable, negative for all pituitary adenoma/hormone markers incuding PIT-1/T-PIT/SF1.
Molecular: Recurrent HRAS mutations and MAPK pathway mutations, some BRAF V600E, some MEN1 frameshift mutations.
Granular cell pituicytoma
Subtype of pituicytoma with large cells that have granular cytoplasm.
Immunohistochemistry: TTF1+, S100 +, Galectin-3 +, EMA +, GFAP variable, negative for all pituitary adenoma/hormone markers incuding PIT-1/T-PIT/SF1.
Ependymal Pituicytoma
Rare subtype of pituicytoma with recrudescence of ependymal rosettes and elongated ependymal-like cells.
Immunohistochemistry: TTF1+, S100 +, Galectin-3 +, EMA +, GFAP variable, negative for all pituitary adenoma/hormone markers incuding PIT-1/T-PIT/SF1.
Pituicytoma, NOS
Subtype of pituicytoma which represents the “default” unless other cytologic characteristics are present. Sheets and short fascicles of spindle, bipolar tumor cells, sometimes in a storiform pattern. Often display this pale eosinophilic, slightly bubbly cytoplasm.
Immunohistochemistry: TTF1+, S100 +, Galectin-3 +, EMA +, GFAP variable, negative for all pituitary adenoma/hormone markers incuding PIT-1/T-PIT/SF1.
Crooke cell adenoma
Rare subtype of secretory corticotroph adenomas, belonging to the T-PIT family of pituitary adenomas, and representing 5-10% of patients with Cushing disease. Has worse clinical outcomes compared to other corticotroph tumors.
Morphologically, display unique features including perinuclear/ring-like cytokeratin deposition, sub-membranous localization of PAS-positive secretory granules, peripheral cytoplasm displacement, and hyalinization.
IHC: T-PIT +, ACTH +, PIT1 negative, SF1 negative. Be sure to stain with PAS and CAM5.2 to assess for the above staining pattern.
Approach to Pituitary NETs
Hormones used to stain:
ACTH
TSH
GH
Prolactin
FSH and LH
GATA3 in pituitary NETs
Positive in thyrotroph tumors and gonadotroph tumors as well as in mature plurihormonal PIT-1-lineage tumors and sometimes immature plurihormonal PIT-1-lineage tumors.
ER in pituitary NETs
Positive in lactotroph tumors, acidophil stem cell tumors, gonadotroph tumors, mature plurihormonal PIT-1-lineage tumors, and sometimes immature PIT-1-lineage tumors.
Acidophil stem cell tumor
Rare subtype of secretory prolactin adenomas, belonging to the PIT-1 family of pituitary adenomas.
Morphologically characterized by diffuse oncocytic cytology with variable intracytoplasmic vacuoles reflecting dilated or giant mitochondria. Scattered fibrous bodies can sometimes be identified.
IHC: PIT-1 +, ER +, prolactin +, GH +/- , TPIT negative
Utility of p27 in pituitary adenomas
Primarily useful in corticotrophs.
Nuclear p27 tends to be preserved in non-secretory corticotrophs and lost in secretory corticotrophs.
Gonadotroph tumor
You can tell this is going to be a gonadotroph even without doing the FSH and LH, since it is already positive for SF1 / GATA3 / ER.
Gonadotroph tumor is the only mature pituitary tumor which is negative for both T-PIT and PIT-1, instead expressing SF1.
What is the most common type of pituitary adenoma?
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Pituitary blastoma
One of the neoplasms pathognomonic for DICER1 syndrome.
Early childhood tumor characterized by Rathke-type epithelium, small blastema-like stromal cells, true rosettes, and large glandular structures / pituitary secretory-type cells.
Molecular shows DICER1 mutation.
Meningioma
Grade 1, meningothelial-type
