Neurosurgery notes/Tumours/Sellar tumours/Spindle cell oncocytoma

Spindle cell oncocytoma

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Sellar tumours

General

  • A spindled to epithelioid, oncocytic, non-neuroendocrine neoplasm of the pituitary gland.
  • Spindle cell oncocytoma is a low-grade, non-functional neoplasm of the sellar region.
  • It is thought to arise from the pituicytes of the posterior pituitary or infundibulum.

Definition

  • Essential criteria
    • Spindled or epithelioid tumour with eosinophilic, granular cytoplasm.
    • Sellar or suprasellar location.
    • Nuclear thyroid transcription factor 1 (TTF1) expression.
    • Absence of pituitary hormone and transcription factor expression.
    • Absence of neuronal and neuroendocrine marker expression.
  • Desirable criteria
    • Absence of interspersed reticulin fibres.
    • Antimitochondrial antigen (such as MU213-UC) immunoreactivity.

Numbers

  • 0.4% of all sellar tumours
  • 25 cases have been reported
  • Adults
    • 50-60 years
    • mean age of approximately 61.6 years.
  • There is a reported slight female predominance.

Grade

  • These are considered low-grade, slow-growing tumours

Histopathology

Macroscopy

  • Indistinguishable from pituitary adenoma.
  • Large tumours
    • Average craniocaudal dimension of 2.5-3 cm
    • Maximum reported size of 6.5 cm
  • Vary from soft, creamy, and easily resectable lesions to firm tumours that adhere to surrounding structures
  • Infrequently can destroy the sellar floor
  • Haemorrhage may occasionally be observed within the tumour.
  • Texture varies from firm and vascular to similar to normal brain, and the colour is typically grey to yellow.

Microscopy

  • The tumour is composed of interlacing fascicles or poorly defined lobules of spindle to epithelioid cells.
  • Neoplastic cells possess eosinophilic, variably granular cytoplasm due to increased mitochondrial content.
  • Oncocytic changes can be focal or widespread.
  • Other patterns may include whorls, myxoid changes, clear cells, and follicle-like structures.
  • Nuclear atypia is usually mild to moderate, although marked pleomorphism is occasionally seen.
  • Focal infiltrates of mature lymphocytes are common.
  • Ki-67 proliferation index low 3% (1-8%)
 
Fig. 17.22 Spindle cell oncocytoma. A The lesion is composed of interlacing fascicles of spindle cells with eosinophilic cytoplasm and mildly to moderately atypical nuclei. B The Ki-67 proliferation index is usually low.
(A) The lesion is composed of interlacing fascicles of spindle cells with eosinophilic cytoplasm and mildly to moderately atypical nuclei. (B) The Ki-67 proliferation index is usually low.
Fig. 17.23 Spindle cell oncocytoma. A Clear-cell appearance of the tumour cells arranged within a nested pattern. changes may be variable within a given tumour. B Some examples have pleomorphic nuclei. C Oncocytic
(A) Clear-cell appearance of the tumour cells arranged within a nested pattern. (B) Some examples have pleomorphic nuclei. (C) Oncocytic changes may be variable within a given tumour.

Immunophenotype

  • +
    • Vimentin
    • S100 protein
    • BCL2
    • EMA
      • EMA expression can vary from weak and focal to diffuse
    • Antimitochondrial antibody MU213UC clone 131-1
    • Nuclear staining for TTF1
    • GFAR CD44
    • GFAP
    • Nestin
    • Alphacrystallin B chain
    • Galectin-3 and annexin A1 are also commonly expressed
      • Although these markers are non-specific, they initially suggested a link to the folliculostellate (ant. Pituitary) cell but later was then refuted
  • -
    • Neuroendocrine markers (synaptophysin, chromogranin A)
    • Pituitary hormones.
    • CAM 5.2
    • Transcription factors such as PIT1 or SF1

Genetic features

  • Evidence suggests activation of the MAPK/ERK and PI3K/AKT pathways.
  • Genetic alterations identified include mutations in HRAS, SND1, FAT1, and occasionally BRAF p.V600E.
  • Recent studies link these tumours to altered metabolic genotypes related to lipid metabolism and the Krebs cycle.

Cells of origin

  • Derived from pituicytes, showing shared histogenesis with pituicytoma and granular cell tumour of the sellar region.

Localisation

  • They arise along the length of the posterior pituitary and infundibulum.
  • Most form suprasellar or sellar/suprasellar masses.
  • Extension into the cavernous sinus or invasion of the sellar floor is possible.

Clinical features

  • Presentation is indistinguishable from other regional lesions: headaches, visual field defects, and hypopituitarism.
  • Visual disturbances
    • Most common
  • Pituitary hypofunction
    • ACTH
      • Cortisol deficiency
        • Severe: loss of peripheral vascular tone → vascular collapse → death
        • Moderate: Vascular tonacity failure → postural hypotension and tachycardia.
        • Mild/chronic: lassitude, fatigue, anorexia, weight loss, decreased libido, hypoglycemia, and eosinophilia
    • GH
      • Child: Short stature
      • Adults:
        • Changes in body composition (fat mass>lean body mass),
        • Decreased BMD,
        • Impaired quality of life,
        • Increased mortality rates.
    • Gonadotrophins (FSH/LH)
      • Male:
        • Infertility
        • Decreased testosterone secretion →
          • Decreased energy
          • Dec. libido
          • Hot flashes
          • Dec. muscle mass (and perhaps strength) after many years
      • Female: ovarian hypofunction → decreased estradiol secretion.
        • Irregular periods or amenorrhea,
        • Anovulatory infertility,
        • Hot flashes,
        • Vaginal atrophy (final)
    • TSH:
      • Fatigue, cold intolerance, decreased appetite, constipation, facial puffiness, dry skin, bradycardia, hyporeflexia, and anaemia.
  • Pituitary stalk effect
    • Mechanism
      • Compression of pituitary stalk → impaired delivery of dopamine to the pituitary → dis-inhibition of lactotrophs → hyperprolactinemia
      • Supra sellar tumours release factors (sub P, Neurokinin A) → stimulate prolactin secretion
    • Presentation
      • Oligomenorrhoea or amenorrhoea
      • Hyperprolactinaemia
  • Diabetes insipidus is reported to be uncommon.

Radiology

  • General
    • Indistinguishable from clinically non-functioning pituitary adenomas on imaging.
  • CT
    • Reported as having the appearance of a solid mass isodense to the brain parenchyma.
  • MRI
    • T1/T2:
      • Solid mass
      • Isointense to the brain parenchyma on T1
      • Linear flow voids: represent blood vessels
      • Hypointense foci: thought to represent hemosiderin deposits
      • Calcification may be seen on CT imaging
    • T1 C+ (Gd):
      • Intense heterogeneous early enhancement, in contradistinction to macroadenomas, which enhance more slowly and not as avidly

Management

  • Primary management consists of gross total surgical excision.
  • Targeted therapy using MAPK/ERK signalling pathway inhibitors may be an option for rare cases demonstrating BRAF mutations.

Prognosis

  • These are typically benign, slow-growing tumours that are curable by complete resection.
  • There is a higher frequency of recurrence in spindle cell oncocytoma compared to pituicytoma or granular cell tumour.
  • Malignant transformation and distant metastases have not been reported.
  • 1/3 of cases have recurred, after 3-15 years
  • Incomplete resection is a risk factor for recurrence.
    • Moderate tumour volume and absence of invasion into surrounding structures facilitate complete resection,
    • Hypervascularity inc. risk of incomplete resection
  • Recurrent tumours can
    • Follow a more aggressive course,
    • Has higher Ki-67 proliferation index and necrosis

Differential diagnosis

  • Pituitary adenomas
    • Spindle cell oncocytomas lack Immunoreactivity for neuroendocrine markers and pituitary hormones.
  • Craniopharygioma
    • Recurrent intratumoural bleeding leads to an erroneous preoperative diagnosis of craniopharyngioma
    • The rich tumoural blood supply can be seen on MR angiography is said to come from bilateral internal carotid arteries