PITUITARY INCIDENTALOMAS - 05/09/11
Résumé |
As is true for technologic advancements in general, advancements in the field of endocrinology have often been associated with unintended consequences.89 For example, the identification of preclinical or subclinical disease occurs as a result of the extensive use of sophisticated diagnostic tools. The dilemma faced by endocrinologists when presented with an asymptomatic pituitary lesion is to distinguish the vast majority of benign clinically insignificant incidentalomas from other pituitary masses that require further therapy, such as hormone-secreting tumors or malignant lesions. Clinicians are increasingly encountering incidental findings on CT and MR imaging scanning consistent with the diagnosis of a pituitary microadenoma.34, 64, 66, 69, 85 The prevalence of pituitary incidentalomas found by CT ranges from 3.7% to 20% and the prevalence found by MR imaging is 10%.22, 66 Autopsy studies have revealed a prevalence ranging from 1.5% to 26.7% for pituitary adenomas less than 10 mm in diameter (microadenomas).66 These tumors are not associated with clinical signs or obvious hormonal abnormalities and remain undiagnosed during the subject's lifetime. Although the vast majority of the lesions identified at autopsy undoubtedly represent microadenomas, the differential diagnosis of a sellar mass is extensive and includes the following37:
• | Pituitary adenoma
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• | Other tumors
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• | Inflammation
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• | Vascular lesions, such as aneurysms |
Studies of radiologic-pathologic correlation are limited.20, 68 In the series reported on by Hall and co-workers,39 high-resolution MR imaging scans of 100 normal volunteers were randomly mixed with scans of 57 patients with surgically confirmed Cushing's disease. In 6 of the 57 patients with Cushing's disease, a hypointense lesion on preoperative MR imaging did not correspond to the site of a microadenoma at surgery, resulting in a false-positive rate of 11%. Based on the criterion of agreement by at least two of three radiologists in the study, 10% of normal subjects had findings consistent with pituitary microadenoma. Among these healthy volunteers, three women had elevated serum levels of growth hormone. Similar findings have been reported with high-resolution MR imaging in another small series.23 These reports highlight the need for additional studies to determine the specificity of high-resolution imaging and methods to reduce the variation in radiologic interpretation. Routine CT and MR imaging scanning using low-resolution techniques have sensitivities much lower than the 10% sensitivity of high-resolution pituitary imaging. In fact, a study of 1000 normal volunteers who underwent MR imaging as part of a National Institutes of Health study protocol identified no pituitary tumors.44 As radiologic techniques improve, it can be anticipated that as many as 10% of patients undergoing these procedures for unrelated reasons will have a pituitary microadenoma discovered incidentally. Incidentally discovered macroadenomas are far less common. In a large compilation of autopsy series encompassing more than 10,000 subjects, only three macroadenomas (≥10 mm in diameter) were found.66 In another study of 3550 consecutive CT scans, seven patients with incidentally discovered pituitary macroadenomas were found, resulting in a prevalence rate of 0.20% (95% confidence interval, 0.05% to 0.35%).70 Similar results were reported in a population-based study of 3672 subjects aged 65 years or older. Six pituitary macroadenomas were found, of which five had not been previously diagnosed.98
Pituitary tumors that are symptomatic as a result of either hormonal excess or mass effect are rare. Epidemiologic studies show a prevalence of about 20 cases per 100,000 persons and an incidence of 2 per 100,000 [see Table 1].2, 38, 76 In an Italian study, the total prevalence of pituitary tumors at the end of 1986 was 19.9 per 100,000 persons, and the incidence was 1.55 per 100,000.2 Fewer than 50% of the diagnosed cases were microadenomas. Screening studies show that prolactinomas, the most common hormone-secreting tumors of the pituitary, have a prevalence of less than 5 cases per 10,000 persons.4, 60, 84 Not all prolactinomas are symptomatic. Acromegaly and Cushing's disease are less common, with prevalences of 7 cases per 100,000 persons and 4 cases per 100,000 persons, respectively, although growth hormone hypersecretion from pituitary tumors has been observed in the absence of clinical findings.1, 4, 14, 30, 35, 49 The prevalence of pituitary tumors that secrete TSH, LH, or FSH is even lower. An important limitation of these data and the data from other population-based studies is their reliance on clinically diagnosed cases. Epidemiologic data, although limited, strongly suggest that medically significant lesions, that is, lesions that are hormonally active and produce clinical disease, are uncommon. Pituitary tumors that do not secrete hormones do not cause morbidity until they become large and cause pituitary hormone deficiency, hyperprolactinemia owing to pituitary disinhibition, neurologic changes such as visual field defects, or some combination of these effects.
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| Address reprint requests to David C. Aron, MD, MS, Education Office 14(W), Louis Stokes Cleveland VA Medical Center, 10701 East Boulevard, Cleveland, OH 44106, e-mail: david.aron@med.va.gov |
Vol 29 - N° 1
P. 205-221 - mars 2000 Retour au numéro
Article précédent
- THYROID INCIDENTALOMAS : Prevalence, Diagnosis, Significance, and Management
- Bartolome Burguera, Hossein Gharib
- MANAGEMENT OF PITUITARY INCIDENTALOMAS : A Survey of British and American Endocrinologists
- Trevor A. Howlett, Julie Como, David C. Aron
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