Ectopic Pituitary Adenoma



Ectopic Pituitary Adenoma


Lester D. R. Thompson, MD





Key Facts


Terminology



  • Benign pituitary gland neoplasm occurring separately from and without involvement of sella turcica (a normal anterior pituitary gland)


Clinical Issues



  • Very rare in ectopic sinonasal tract locations



    • Sphenoid sinus > > > nasopharynx or nasal cavity


  • Mean: 50 years


  • Female > Male (2:1)


  • Presents with space-occupying effects or endocrine abnormalities


  • Complete surgical removal, followed by medical/hormone manipulation


Image Findings



  • Intrasphenoidal mass with erosion of sellar floor


  • Early, intense, but heterogeneous enhancement


Microscopic Pathology



  • Submucosal location of unencapsulated tumor


  • Tumors arranged in many patterns


  • Tumor groups separated by delicate fibrovascular septae


  • Monotonous population of round to polygonal epithelial cells


Ancillary Tests



  • Positive: Keratin, chromogranin–A &/or –B, synaptophysin, CD56, NSE, specific hormones


Top Differential Diagnoses



  • Olfactory neuroblastoma, Ewing/PNET, neuroendocrine carcinoma, squamous cell carcinoma, lymphoma, meningioma







There is a submucosal location to this unencapsulated ectopic pituitary adenoma. The surface epithelium is intact image and uninvolved by the tumor, showing a well-developed Grenz zone of separation.






This very cellular tumor shows solid to vaguely trabecular architecture, separated by delicate fibrovascular septae image. The neoplastic population is monotonous, showing eccentrically located, round nuclei.


TERMINOLOGY


Definitions



  • Benign pituitary gland neoplasm occurring separately from and without involvement of sella turcica (a normal anterior pituitary gland)



    • Direct extension from intrasellar neoplasm is much more common (seen in about 2% of pituitary tumors) and must be excluded


ETIOLOGY/PATHOGENESIS


Pathogenesis



  • Anterior pituitary primordium appears at about 4 weeks of embryogenesis


  • During 8th developmental week, pituitary divides into sellar and pharyngeal parts



    • Supradiaphragmatic attachment to pituitary stalk


    • Cephalic invagination of Rathke pouch (infrasellar)


  • Migration into sphenoid or pharynx can be seen, often along craniopharyngeal canal



    • Ectopic pituitary adenomas are thought to be derived from these embryologic remnants along the migration path of Rathke pouch


    • Leptomeningeal locations are common but still intracranial


  • Fully functional tissue in these ectopic locations is compatible with normal life



    • Pharyngeal pituitary begins hormone function at 17th-18th week, up to 8 weeks after sellar pituitary


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Pituitary adenomas account for 10-15% of intracranial neoplasms


    • Very rare in ectopic locations within upper aerodigestive tract


  • Age



    • Wide range: 16-84 years


    • Mean: 50 years


  • Gender



    • Female > Male (2:1)


Site



  • Sphenoid sinus > > > cavernous sinus > 3rd ventricle > nasopharynx, nasal cavity, clivus > > petrous temporal bone



    • Must exclude “invasive sellar” tumors or direct extension from intracranial primary


    • Intact pituitary sellar is usually required


Presentation



  • Space-occupying effects



    • Nasal obstruction or airway obstruction


    • Headaches


    • Bloody nasal discharge or epistaxis


    • Cerebrospinal fluid leakage (clear fluid)


    • Visual field defects (diplopia)


  • Endocrine abnormalities seen in around 50% of patients



    • Cushing disease (adrenocorticotrophic hormone [ACTH]) most common


    • Acromegaly (growth hormone [GH])


    • Hyperthyroidism (thyroid-stimulating hormone [TSH])


    • Amenorrhea, hirsutism, impotence (prolactin [PRL])


    • Diagnosis unsuspected in functionally silent tumors


  • Chronic sinusitis


  • Rarely, cranial nerve(s) paralysis


Laboratory Tests



  • All ectopic hormones can be measured serologically or via stimulation/suppression testing



    • ACTH, GH, TSH, prolactin, cortisol


    • Releasing hormones can also be measured



Treatment



  • Surgical approaches



    • Surgery is treatment of choice but only if completely removed



      • Transnasal/transsphenoidal approach


  • Drugs



    • Medical/hormonal manipulation



      • Dopamine-agonists (bromocriptine), somatostatin analogs (octreotide), corticosteroids (hydrocortisone, prednisone), thyroxine


  • Radiation



    • Stereotactic radioablation, usually for larger or incompletely removed tumors


    • Conventional radiation therapy


Prognosis



  • Excellent prognosis with control of endocrine abnormalities after complete surgical resection



    • Morbidity associated with hormonal manifestations and local invasion (bone or cranial cavity extension)


  • Recurrence may develop in large tumors


  • Malignant transformation is exceptionally rare


  • Metastases are not reported


IMAGE FINDINGS


Radiographic Findings



  • Thin section MR (with and without contrast) or CT yields best results


  • Intrasphenoidal mass with erosion but usually not expansion of sellar floor



    • Sella may be involved by upward extension, although usually normal


  • Usually show early, intense, but heterogeneous enhancement


  • CT and MR define extent and location of tumor


  • Diagnostic procedures usually suggest another type of neoplasm



    • Chordoma, nasopharyngeal carcinoma, or metastatic tumor


MR Findings



  • T1WI: Rounded, isointense mass within sphenoid sinus; usually fills sinus; partially empty sella



    • Post contrast, mass will strongly enhance, although can be heterogeneous


  • T2WI: Isointense mass within sphenoid



    • FLAIR technique results in hyperintense signal

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Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Ectopic Pituitary Adenoma

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