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Pituitary Microadenoma

Last Updated: March 27, 2020

Open Table of Contents: Pituitary Microadenoma

Figure 1: A tiny pituitary adenoma is visible on early postcontrast images (left) as a nodule showing less enhancement than surrounding pituitary tissue in the left inferolateral aspect of the pituitary gland (yellow arrow). This adenoma becomes invisible on the more delayed postcontrast images (right) as the lesion and the pituitary gland become more similar in their degree of contrast enhancement.

Basic Description

  • Primary tumor of the adenohypophysis of various cell line differentiations, ≤10 mm in size


  • Low-grade tumors, World Health Organization (WHO) I
  • Well differentiated, slow growing or nongrowing
  • May secrete hormones according to the cell of origin, most commonly prolactin

Clinical Features

  • Usually incidental (nonfunctioning)
  • May have symptoms related to hormone secretion (secretory)
    • Prolactinoma is most common
      • Women: irregular menses, amenorrhea, galactorrhea
      • Men: hypogonadism, decreased libido
    • Growth hormone secreting (acromegaly)
    • Adrenocorticotropic hormone (ACTH) secreting (Cushing’s disease)
    • Thyroid-stimulating hormone (TSH) secreting (hyperthyroidism)
  • 10% of all patients on autopsy series
  • More common in syndromes such as multiple endocrine neoplasia type 1 (MEN1), McCune-Albright, Carney complex, familial isolated pituitary adenoma syndrome (FIPA)
  • Pituitary apoplexy is a rare but serious complication


  • General
    • Small intrasellar mass <10 mm in size
    • May be cystic, proteinaceous, or hemorrhagic
    • May demonstrate elevated contour on the superior margin of the affected side of the pituitary gland
    • May deviate the infundibulum away from the side of the microadenoma
  • CT
    • Usually not visible, nonrevealing
    • Cystic or hemorrhagic lesions may be visible as tiny hypodense or hyperdense lesions
    • May see slight deviation of the infundibulum
    • Thin-cut CT may be helpful to delineate sphenoid sinus bony anatomy for surgical planning
  • MRI
    • T1WI: Usually not visible unless cystic (hypointense) or hemorrhagic/proteinaceous (hyperintense)
    • T2WI: variable, hyperintense if cystic
    • FLAIR: variable, hyperintense if cystic
    • DWI: usually not visible or obscured by adjacent sphenoid sinus/bone susceptibility artifact
    • T1WI+C: Usually enhances similar to surrounding pituitary gland on routine postcontrast imaging. On dynamic postcontrast images through the sella, microadenomas may be more visible at a time point during which they enhance less than normal pituitary tissue because of their comparatively delayed enhancement pattern.
    • Advanced Imaging: these lesions are too small to appear on most advanced imaging modalities (MR spectroscopy, MR perfusion)
  • Conventional Angiography
    • Inferior petrosal sinus sampling (IPSS) is more accurate for identifying ACTH-secreting microadenomas than imaging alone
  • Imaging recommendations: MRI without and with contrast with detailed images of the sella, including dynamic coronal postcontrast sequences. Thin-cut CT of the sinuses or sella may be helpful for delineating sphenoid sinus anatomy prior to transsphenoidal resection and during intraoperative navigation

For more information, please see the corresponding chapter in Radiopaedia.

Contributor: Rachel Seltman, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.01.34


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Chen CC, Carter BS, Wang R, et al. Congress of Neurological Surgeons systematic review and evidence-based guideline on preoperative imaging assessment of patients with suspected nonfunctioning pituitary adenomas. Neurosurgery. 2016;79: E524-E526.

Osborn AG. Osborn's Brain: Imaging, Pathology, and Anatomy. Salt Lake City: Amirsys, 2013: 699-705.

Raff H. Cushing syndrome: update on testing. Endocrinol Metabolism Clin North Am. 2015;44: 43-50.

Vance M. Pituitary adenoma: a clinician's perspective. Endocrine Prac. 2008;14: 757-763.

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