Neoplasms in the region of the pituitary fossa

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Neoplasms in the region of the pituitary fossa


Neoplasms in the region of the pituitary fossa may arise in the pituitary gland itself, the sphenoid bone that surrounds the fossa, or the suprasellar region (Figs 44.1, 44.2). Structures in the suprasellar region and adjacent to the pituitary fossa include the hypothalamus, optic chiasm, nasal sinuses, and cavernous sinuses and their contents.




Common neoplasms in this region are:



Uncommon neoplasms in this region are:



Other neoplasms are rare.



The pituitary gland weighs about 600 mg and consists mainly of the adenohypophysis (anterior lobe) and the neurohypophysis (posterior lobe) (Figs 44.344.6); the pars intermedia is poorly developed in man.






Adenomas are the commonest neoplasms in the pituitary gland and are derived from cells in the adenohypophysis. Neoplasms of neurohypophyseal origin are very rare.



PITUITARY ADENOMAS


Pituitary adenomas are derived from secretory cells in the adenohypophysis. Some adenomas secrete peptides in an unregulated manner and may therefore produce abnormal endocrine effects in addition to causing mass effects in the region of the pituitary fossa (Fig. 44.7).






MACROSCOPIC APPEARANCES


Pituitary adenomas are soft and have a beige or cream color. Discussion between the neurosurgeon and pathologist at the time of operation sometimes raises the possibility of an alternative diagnosis (e.g. a tough mass is more likely to be a meningioma).


By convention, macroadenomas and microadenomas have diameters above and below 10 mm, respectively. Most microadenomas diagnosed in life are ACTH-cell adenomas and PRL-cell adenomas presenting early with endocrine effects. Histopathologic assessment of surgically treated microadenomas requires a thorough examination of all submitted tissue.




MICROSCOPIC APPEARANCES



image PITUITARY ADENOMAS




image The commonest neoplasms in the region of the pituitary fossa, and represent 10–15% of intracranial neoplasms.


image Have an incidence ranging from 1–15/100 000 in different series.


image Most common in the third to sixth decades.


image Show a female:male ratio of approximately 2:1 in younger patients.


image May be an incidental finding in approximately 10% of elderly people according to some necropsy series (40% of these neoplasms are prolactinomas).


image May present with the effects of increased peptide production (i.e. acromegaly or gigantism due to excess GH, Cushing syndrome due to excess ACTH, amenorrhea, galactorrhea, or impotence due to excess PRL, hyperthyroidism due to excess TSH).


image May present with mass effects (i.e. headache, compression of the optic chiasm, (other) cranial nerve palsies, compression of the othalamus, hypopituitarism, pituitary infarction). Pituitary peptide deficiencies preceding complete hypopituitarism tend to occur in sequence (i.e. GH → FSH/LH → TSH → ACTH).


image Can compress the pituitary stalk and thereby compromise transport of PRL inhibitory factor (dopamine) to the adenohypophysis, resulting in an elevated PRL level (‘stalk effect’), but PRL concentrations seldom exceed 200 mg/L in these circumstances.


image May present acutely with mass effects when they undergo infarction or hemorrhage.






The histology of pituitary adenomas is varied (Table 44.1). Many adenomas consist of small, oval, or polyhedral cells. These may be arranged in monotonous sheets or show a variety of acinar, papillary, trabecular, or other patterns (Figs 44.944.11). The nuclei of neoplastic cells are generally round or oval and contain the stippled chromatin typical of neuroendocrine neoplasms. Tiny nucleoli may be evident. Cytologic pleomorphism and mitotic figures may be present, but do not necessarily signify aggressive biologic behavior (Fig. 44.12). Invasion of local structures (Fig. 44.13), particularly the dura, is not infrequent, even by adenomas with bland cytologic features.









Dystrophic calcification and eosinophilic (amyloid) bodies are strongly associated with prolactinomas (Fig. 44.14). Long-term treatment of prolactinomas with bromocriptine before surgical resection produces fibrosis.


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Jul 20, 2016 | Posted by in NEUROLOGY | Comments Off on Neoplasms in the region of the pituitary fossa

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