Definition

A pituitary incidentaloma is defined strictly as a ‘totally asymptomatic non- functional tumour, clinically and biochemically silent, which was discovered incidentally in a patient who is asymptomatic’ or, less strictly, a pituitary mass discovered in the course of evaluation for an unrelated problem . Based on the second definition, the term incidentaloma may not be appropriate to many of these lesions, as an incidentally detected macroadenoma may still be clinically relevant.

Frequency of Detection

Autopsy Studies

The mean frequency of adenoma detection in the largest collection of autopsy case series, which examined 18 902 pituitaries, was 10.7% (ranging from 1.5% to 31%). All but seven of these lesions had a diameter smaller than 10 mm, indicating that almost all of the pituitary adenomas found in autopsy series are microadenomas. There was also no age or gender preponderance. A detailed analysis of immunohistochemical staining of 334 pituitary adenomas in 316 pituitaries out of 3048 autopsy cases revealed 39.5% immunopositivity for prolactin, followed by 13.8% for ACTH, 6.6% for gonadotropins, 2.1% for growth hormone (GH), and 0.6% for thyroid- stimulating hormone (TSH) and α- subunit, respectively. Negative immunostaining was reported in 22.5%, while plurihormonal adenomas accounted for 2.7%.

imaging Studies

 The detection of incidental pituitary lesions on imaging depends on the modality used, the administration of contrast agents and the slice thickness used. Pituitary incidentalomas have been reported with increasing frequency paralleling the advances in imaging techniques and the wider use of brain scans. The prevalence of pituitary incidentalomas found by CT ranges from 3.7% to 20% and of those found by MRI is 10%. Similar to autopsy series, radiological studies on subjects undergoing imaging for reasons not related to a pituitary problem have found frequency of macroadenomas between 0.16% and 0.20%.

Differential Diagnosis

The most common aetiology of pituitary incidentalomas is pituitary adenomas, the majority (>75%) of which are non- functioning. Apart from adenomas, the differential diagnosis of pituitary incidentaloma is extensive (Box 1).

Box1. Differential diagnosis of pituitary incidentalomas

Diagnostic evaluation

A cost- effective approach is required to exclude potentially harmful conditions, as well as to decrease patient anxiety.

Imaging techniques are helpful in the diagnostic evaluation of an incidentally found pituitary mass. MRI has been proven to be more sensitive than CT for the detection of pituitary adenomas. CT is superior in detecting calcifications and is, therefore, helpful for the diagnosis of craniopharyngiomas and meningiomas. There are no studies providing correlation between MRI and pathological features of pituitary masses. Nevertheless, specific MRI features of a number of sellar masses (including meningiomas, metastatic disease, craniopharyngiomas, Rathke’s cleft cysts, arachnoid cysts, hypophysitis, abscess) may be useful in the differentiation from an adenoma.

Given that the most common lesion in the sellar area is a pituitary adenoma, assessment for hormonal hypersecretion is recommended. This includes clinical evaluation for relevant manifestations combined with biochemical screening for hormonal excess:

a) Prolactin (2– 3 measurements) for prolactinomas.

b) Insulin- like growth factor- I, which in cases of suspected acromegaly could be combined with an oral glucose tolerance test.

c) 24- hour urine free cortisol and overnight dexamethasone sup pression test for Cushing’s disease.

 d) TSH, free T4, and free T3 for TSH- secreting tumour.

 e) FSH, LH, alpha subunit, oestradiol, or testosterone for functioning gonadotroph adenomas.

Smaller incidentalomas (5 mm or less in diameter) do not generally compromise the pituitary function and routine screening may not be necessary; however, evaluation for hypopituitarism is recommended for patients with larger lesions. Assessment for the presence of diabetes insipidus is suggested particularly when there is suspicion of craniopharyngiomas and pituitary metastases.

All patients who have a pituitary lesion abutting or compressing the optic nerves or chiasm on MRI, should undergo a formal visual field (VF) examination.

natural History

 The studies on the natural history of pituitary incidentalomas are limited. The shortcomings of currently available literature include patient heterogeneity, relatively small patient series, and lack of prolonged follow- up. Their results including masses of various pathologies are summarized in Table 1. Overall, the published data suggest that lesions smaller than 1 cm follow a benign course. In contrast, masses greater than 1 cm are associated with higher risk of enlargement often leading to pressure effects and requiring neurosurgical intervention. These data are in accord with the reported outcomes of non- operated presumed non- functioning pituitary adenomas (Table 2 and Figure 1). Indeed, a systematic review and meta- analysis of 11 cohort studies of significant heterogeneity showed that non- functioning pituitary adenomas and incidentalomas which were bigger than 1 cm and solid had a greater event rate of tumour growth compared to smaller and cystic lesions, albeit the quality of evidence was deemed low.

Table1. Natural history of pituitary incidentalomas

Table2. Natural history of non- operated presumed non- functioning pituitary adenomas

Fig1. Natural history of (a) microadenoma versus (b) macroadenoma. From Karavitaki N, Collison K, Halliday J, et al. What is the natural history of nonoperated nonfunctioning pituitary adenomas? Endocrinol (Oxf). 2007; 67:938–943. Reproduced with permission from John Wiley and Sons.

It is noteworthy that majority of the reported studies have a follow- up period of less than 5 years, a duration which is deemed short considering the natural history of pituitary tumours. Hence, more studies with longer observation periods are needed to clarify the behaviour and outcomes of pituitary incidentalomas.

Despite the rare occurrence of pituitary apoplexy, its risk should always be taken into consideration, particularly in patients exposed to predisposing factors (e.g. anticoagulation).

The potential of incidentally found adenomas to become hormonally active at a later stage has not been fully elucidated and reliable data on the chance of developing relevant endocrinopathy is lacking.

Management

The Endocrine Society Clinical Practice Guideline recommends surgery by an experienced pituitary surgeon for patients with a pituitary incidentaloma who present with VF deficit or other visual abnormalities due to the lesion, lesion abutting, or com pressing optic nerves or chiasm on MRI, pituitary apoplexy or hypersecreting tumours other than prolactinomas. In cases not meeting the aforementioned criteria, conservative management with regular follow- up is recommended. As the long- term natural history of incidentally detected pituitary masses is still unclear, the current consensus is largely based on expert opinion.

Our proposed algorithm for the initial evaluation and management of these lesions is shown in Figure 2. Since the optimum duration of imaging surveillance is unknown, decisions on monitoring of a mass not showing enlargement 5 years after its detection should be individualized. Finally, cost remains an important factor in determining the optimum follow- up strategy of pituitary incidentaloma. Randall et al. reported the total cost of endocrine tests, imaging, and physician fees incurred during a year of follow- up of pituitary incidentaloma to be USD 6215.28 for males and USD 6061.78 for females. This was expected to account for a conservative estimate of nearly USD 7 million on the United States healthcare system in year 2005. It is important to note that this estimate does not include expenditure involved during further follow- ups. Hence, the cost- effectiveness of the suggested or other approaches remains to be elucidated.

Fig2. Algorithm for the evaluation and management of pituitary incidentalomas.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم الشؤون الدينية يطلق الدورة التطويرية والفقهية الخامسة لملاكات العتبة العباسية المقدسة

قسم الشؤون الفكرية ينظّم ختمة قرآنية رمضانية لطلبة العلوم الدينية الأفارقة في النجف

شعبة الخطابة تقيم مجلسا للوعظ والإرشاد في الصحن الشريف تزامناً مع حلول شهر رمضان المبارك

قسم التطوير يختتم دورة إعداد المدربين لملاكات مديرية تربية كربلاء

المزيد

الآخبار الصحية

مفاجأة.. تحسين القدرة على التحمل لا يعتمد العضلات فقط

المرتفعات والأكسجين.. دراسة "مبشرة" لمرضى السكري

علماء يبتكرون "آلية" تتوقع موعد ظهور أعراض الزهايمر

ماذا يحدث لجسمك عند التوقف عن تناول الخضراوات والفواكه؟

المزيد

الآخبار التكنلوجية

رصد "القرش النائم" في أحد أقسى الأماكن على وجه الأرض

أسماك أعماق البحر تكشف نظاما بصريا يتجاوز "المألوف"

زوكربيرغ أمام القضاء في قضية إدمان المراهقين

"علي بابا" تكشف عن نموذج جديد للذكاء الاصطناعي

المزيد

مواضيع ذات صلة

Pathological evaluation of Pituitary carcinomas

Clinical Presentation and Diagnosis of Pituitary carcinomas

Aetiopathogenesis and Pathology of Thyrotropinomas

Cancer and The Environment

Cytogenetic Changes in Cancer

Telomerase as an Oncogene

Activation of Oncogenes by Chromosome Translocation or Fusions

Imaging of the Pituitary: Adenomas

T pit Family of tumours

Pit- 1 Family of tumours

Pituitary Adenomas

Molecular Mechanisms of Carcinogenesis