Incidentally discovered sellar masses (pituitary incidentalomas)
- Peter J Snyder, MD
Peter J Snyder, MD
- Editor-in-Chief — Endocrinology
- Section Editor — Pituitary Disease; Male Reproductive Endocrinology
- Professor of Medicine
- University of Pennsylvania School of Medicine
The frequent detection of unsuspected anatomic abnormalities in many glands ("incidentalomas"), including the pituitary, made possible by the sensitivity of magnetic resonance imaging (MRI), raises the question of how to evaluate patients who have such an abnormality. The causes, evaluation, and treatment of pituitary incidentaloma are discussed here. The causes, clinical presentation, and evaluation of sellar masses are reviewed separately. (See "Causes, presentation, and evaluation of sellar masses".)
The term “pituitary incidentaloma” refers to a previously unsuspected lesion that is detected on an imaging study performed for reasons other than pituitary symptoms or disease. Among adults undergoing imaging studies (computed tomography [CT] or magnetic resonance imaging [MRI]) for reasons other than pituitary symptoms or disease, the frequency of incidentally discovered signal abnormalities (<10 mm) varies among studies from 4 to 20 percent by CT [1-3] and 10 to 38 percent by MRI [4,5].
Not all incidentally discovered sellar masses are pituitary adenomas. In one study of 61 incidentally discovered sellar masses found among 1000 unselected autopsy specimens, there were 37 Rathke’s cleft cysts, 18 pituitary adenomas, and two each of hyperplasia, infarction, and hemorrhage . However, pituitary adenomas are a common finding, as illustrated by a review of 29 autopsy studies that included over 18,000 pituitary glands . The frequency of pituitary adenomas was approximately 10 percent, and nearly all of the adenomas were microadenomas (<10 mm). The frequencies were similar for men and women, and across age groups in adults.
CHARACTERISTICS OF REFERRED PATIENTS
Patients who are referred for evaluation of incidentally discovered magnetic resonance imaging (MRI) signal abnormalities within the sella tend to have larger lesions and a higher incidence of neurologic abnormalities than would be expected from autopsy and MRI series of unselected patients [8,9]. This presumably reflects the selection process of a referral population. In one series of 31 referred patients, 16 had lesions 10 mm or larger . Three of the 31 patients had hormonal abnormalities; two had slightly high serum alpha-subunit concentrations, and two mild hyperprolactinemia (one patient had both). In the largest reported series of incidentally discovered sellar masses, 506 patients were reported from referral centers, in response to a questionnaire, to have incidentally-discovered sellar masses; the majority were >10 mm .
The overall frequency of different types of pituitary adenomas is not known because many large series of incidentally discovered sellar masses intentionally exclude those patients who have lesions that are hypersecreting. In our experience, however, it is common for a sellar mass that is discovered incidentally to be associated, on further evaluation, with obvious clinical consequences, including visual impairment and hormonal hypersecretion. Some of these patients even have obvious clinical manifestations of the hypersecretion (eg, acromegaly) that had been overlooked until the mass was discovered.
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