CNS tumor

Sellar region tumors

Pituicytoma


Resident / Fellow Advisory Board: Meaghan Morris, M.D., Ph.D.
Editorial Board Member: Chunyu Cai, M.D., Ph.D.
Federico Roncaroli, M.D.

Topic Completed: 29 March 2021

Minor changes: 29 March 2021

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PubMed Search: Pituicytoma

Federico Roncaroli, M.D.
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Cite this page: Roncaroli F. Pituicytoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorpituicytoma.html. Accessed November 29th, 2021.
Definition / general
  • Pituicytoma belongs to the group of tumors arising from the neurohypophysis and pituitary infundibulum, together with spindle cell oncocytoma and granular cell tumor
    • These tumors are characterized by the expression of the transcription factor TTF1
    • Pituicytoma probably derives from light and dark normal pituicytes
  • Pituicytoma is regarded as grade I by the World Health Organization classification of central nervous system tumors
Essential features
  • Pituicytoma belongs to the group TTF1 expression tumors of the neurohypophysis and infundibulum
  • Histologic features include fascicles of spindle cells or epithelioid cells expressing TTF1, S100 protein and GFAP
  • Surgical resection is curative; excellent outcome
Terminology
  • Not recommended:
    • Infundibuloma
    • Low grade glioma of sella and suprasellar region
    • Pilocytic astrocytoma
ICD coding
Epidemiology
  • About 0.07% of all primary sellar neoplasms (German Pituitary Registry, Eur J Endocrinol 2007;156:203)
  • About 50% of posterior pituitary tumors (World Neurosurg 2021;145:148)
  • Usually in adults: 40 - 60 years
  • No obvious male or female predominance
  • Exceptional in children (3% of posterior pituitary tumors)
Sites
  • Sella and suprasellar region
Pathophysiology
Etiology
  • Unknown
Clinical features
  • Main signs and symptoms at onset include (World Neurosurg 2021;145:148)
    • Headache
    • Visual field defects
    • Hypopituitarism
    • Occurrence of polydipsia and polyuria (diabetes insipidus) is rare despite the involvement of the infundibulum (3 - 5%)
    • Apoplexy exceptional
    • Rarely causes hypercortisolism or acromegaly without the presence of a synchronous corticotroph or somatotroph pituitary tumors
    • Pituicytoma can also present in association with primary tumors of adenohypophyseal cells (collision tumors)
Diagnosis
  • Evidence of sellar and suprasellar or suprasellar only lesion involving the infundibulum
  • Usually no excess of pituitary hormones
  • Diagnosis made on histology
Laboratory
Radiology description
  • Can be suspected when exclusively suprasellar and the anterior hypophysis is spared
  • Indistinguishable from other clinically nonfunctioning primary sellar tumors when it involves sella and the suprasellar region
  • MRI features: isointense on T1 weighted sequences and often inhomogeneous intensity on T2 weighted sequences; homogenous or heterogeneous contrast enhancement
  • Reference: World Neurosurg 2021;145:148
Radiology images

Contributed by Federico Roncaroli, M.D.
Sagittal postcontrast MRI

Sagittal postcontrast MRI

Prognostic factors
  • Behaves as benign tumor
  • Recurrence can occur when incompletely excised (4% of cases)
  • 1 recurrent case showed nuclear atypia and mitoses (Pathology 2011;43:389)
Case reports
Treatment
Gross description
  • Usually white, gray or light yellow soft tissue fragments; hemorrhagic changes can be seen
Frozen section description
  • Fascicles of spindle cells in fibrillary background reminiscent of glioma
  • Possible ill defined whorls reminiscent of sellar meningioma
  • Bipolar cells similar to schwannoma
Microscopic (histologic) description
  • Sheets and short of fascicles of spindle, bipolar tumor cells; storiform pattern can be present
  • Rarely, epithelioid cells
  • At times, ependymal-like features; very rarely, oncocytic changes
  • Rarely, focal chronic inflammation
  • Absent pericellular reticulin fibers
  • Absent Rosenthal fibers, granular bodies and hyalinzed blood vessel walls
  • Lack of Herring bodies
  • Usually negligible mitotic activity
  • Rarely, increased cellularity, severe nuclear atypia and high mitotic count
  • References: Am J Surg Pathol 2000;24:362, Am J Surg Pathol 2013;37:1694
Microscopic (histologic) images

Contributed by Federico Roncaroli, M.D.
Fascicles of spindle cells

Fascicles of spindle cells

Ill defined whorls

Ill defined whorls

Schwannoma-like features

Schwannoma-like features

Mild nuclear atypia

Mild nuclear atypia

GFAP expression

GFAP expression

TTF1 nuclear expression

TTF1 nuclear expression

Cytology description
  • Aggregates of spindle cells with fibrillary to fine cytoplasm, usually thin walled, delicate vessels and neuropil-like background; features can be reminiscent of meningioma (Diagn Cytopathol 2020;48:342)
Positive stains
Negative stains
Electron microscopy description
Molecular / cytogenetics description
Sample pathology report
  • Pituitary gland / sellar region, surgical excision:
    • Pituicytoma (WHO grade I) (see comment)
    • Comment: Pituicytoma belongs to the group of TTF1 expressing tumors of the posterior hypophysis and infundibulum. It rarely recurs when incompletely removed; follow up is recommended.
    • Microscopic examination shows interlacing fascicles of spindle cells with fibrillary cytoplasm and mildly atypical, slightly hyperchromatic nucleus. Vessels are thin walled. No axons are seen crossing the lesion.
    • Immunohistochemically the tumor cells show TTF1 nuclear expression, diffuse vimentin and S100 expression and expression of GFAP. Immunostains for EMA, synaptophysin and chromogranin are negative.
    • The features are those of a TTF1 expressing tumor of the neurohypophysis and infunbibulum and are consistent with pituicytoma.
Differential diagnosis
Board review style question #1

Middle aged man presented with hypopituitarism. Imaging showed a sellar and suprasellar enhancing lesion. The microscopic image is from the surgical specimen. Which of the following immunostains is typically positive in tumor cells?

  1. Chromogranin
  2. Cytokeratin CAM5.2
  3. Neurofilament
  4. TTF1
  5. Vasopressin
Board review style answer #1
D. TTF1

Comment Here

Reference: Pituicytoma
Board review style question #2
Which of the following is correct regarding pituicytoma?

  1. Frequently recurs
  2. Not responsive to radiotherapy and chemotherapy
  3. Surgery alone can be curative
  4. Usually extensively invasive
Board review style answer #2
C. Surgery alone can be curative

Comment Here

Reference: Pituicytoma
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