CNS tumor
Sellar region tumors
Pituicytoma
Author: Federico Roncaroli, M.D.
Resident / Fellow Advisory Board: Meaghan Morris, M.D., Ph.D.
Editorial Board Member: Chunyu "Hunter" Cai, M.D., Ph.D.
Topic Completed: 29 March 2021
Minor changes: 29 March 2021
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Pituicytoma
Table of Contents
Definition / general | Essential features | Terminology | ICD coding | Epidemiology | Sites | Pathophysiology | Etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Gross description | Frozen section description | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Sample pathology report | Differential diagnosis | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Roncaroli F. Pituicytoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorpituicytoma.html. Accessed May 16th, 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
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
- TTF1 expression indicates an origin from neurohypophysis and infundibulum (Am J Surg Pathol 2013;37:1694)
- Ultrastructural similarities suggest an origin from light and dark pituicytes (Am J Surg Pathol 2013;37:1694)
- Given the low incidence of diabetes insipidus, an origin from the lower infundibulum has been proposed (Pituitary 2012;15:227)
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
- Low serum levels of pituitary hormones
- Increase in prolactin due to pituitary stalk compression
- Occasional increase in growth hormone or ACTH / peripheral cortisol
- References: World Neurosurg 2021;145:148, Endocrine 2020;70:15
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
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)
- Unclear relevance of atypia and increased proliferation as prognostic factors (Acta Neuropathol Commun 2019;7:69)
Case reports
- 26 year old man presented with decreased libido, hypopituitarism and visual disturbances (Neurosurgery 2004;54:753)
- 47 year old woman with a history of Cushing disease and a left sided intrasellar lesion (J Surg Case Rep 2020;2020:rjaa104)
- 61 year old man presented with progressively worsening visual acuity; eupituitary; mixed solid-cystic, intra and suprasellar lesion (Surg Neurol Int 2018;9:145)
- 71 year old man with a previous diagnosis of sellar meningioma; recurrent lesion on surveillance imaging after 16 years (Ann R Coll Surg Engl 2020;102:e87)
Treatment
- Complete surgical excision is curative
- Radiotherapy administered in a few patients; unclear benefits
- References: World Neurosurg 2021;145:148, Pituitary 2012;15:227
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
Ill defined whorls
Schwannoma-like features
Mild nuclear atypia
GFAP 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
- TTF1
- Vimentin, S100
- Variable GFAP (expressed in all cases)
- CD56 (NCAM), galectin3, BCL2, focal SSTR2A (20% of cases)
- Low Ki67 labeling index
- References: Am J Surg Pathol 2000;24:362, Am J Surg Pathol 2013;37:1694
Negative stains
- Pituitary hormones (GH, PRL, ACTH, TSH beta subunit, FSH beta subunit, LH beta subunit and common alpha subunit)
- Pituitary transcription factors (PIT1, SF1 and TPIT)
- Synaptophysin, neurofilament proteins, collagen type IV (absent around single tumor cells)
- EMA
- Cytokeratins
- Vasopressin
- Reference: Am J Surg Pathol 2013;37:1694
Electron microscopy description
- Elongated or oval tumor cells
- Focal accumulations of intermediate filaments
- No interdigitating cell membranes
- No excess of mitochondria
- No desmosomes
- No pericellular basal lamina
- References: Neurosurgery 2004;54:753, Am J Surg Pathol 2013;37:1694
Molecular / cytogenetics description
- Information on molecular profile is limited to 3 cases (Acta Neuropathol Commun 2019;7:69)
- It includes pathogenetic mutations in HRAS, BRAF V600E, NF1 and TSC1
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
- Normal neurohypophysis and infundibulum:
- Vasopressin positive
- Herring bodies and axons absent in pituicytoma
- Spindle cell oncocytoma:
- Granular cell tumor of the posterior pituitary:
- Similar to granular cell tumor in other locations
- Granular cytoplasm
- GFAP negative
- Sellar schwannoma:
- TTF1 negative
- Pericellular collagen IV
- Pilocytic astrocytoma:
- Rosenthal fibers and granular bodies
- Often vascular with features of endothelial proliferation
- Meningioma:
- Pituitary adenoma:
- Rarely, spindle cells
- Chromogranin and synaptophysin positive
- TTF1 negative
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?
- Chromogranin
- Cytokeratin CAM5.2
- Neurofilament
- TTF1
- Vasopressin
Board review style answer #1
Board review style question #2
Which of the following is correct regarding pituicytoma?
- Frequently recurs
- Not responsive to radiotherapy and chemotherapy
- Surgery alone can be curative
- Usually extensively invasive
Board review style answer #2
