Parathyroid adenoma

Posted By Wael Nemattalla
Parathyroid adenoma

71 years old male with high parathormone level.

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  • Wael Nemattalla 2014-01-02 11:38:17

    Parathyroid adenoma





    Parathyroid adenomas are benign tumours of the parathyroid glands and are considered the commonest cause of primary hyperparathyroidism.



    Clinical presentation

    Patients typically present with primary hyperparathyroidism with elevated serum calcium levels and elevated serum parathyroid hormone (parathormone) levels.



    Pathology

    They are usually oval or bean-shaped, but larger adenomas can be multilobulated. The vast majority (upto 87% 2) of adenomas occur as solitary lesions



    Location

    Upto 5% of parathyroid adenomas can occur in ectopic locations. Common ectopic locations include 1.

    • thymus

    • tracheo-oesophageal groove

    • carotid sheath

    • intrathyroidal

    • paraoesophageal



    Radiographic features



    Ultrasound

    Ultrasound is one of most commonly used initial imaging modalities.

    Grey scale

    Most nodules need to be greater than 1cm to be confidently seen on ultrasound. Parathyroid adenomas tend to be homogeneously hypoechoic to the overlying thyroid gland.



    Doppler ultrasound

    Can commonly show a characteristic extrathyroidal feeding vessel (typically a branch off the inferior thyroidal artery 1,6), which enters the parathyroid gland at one of the poles. Internal vascularity is also commonly seen in a peripheral distribution. This feeding artery tends to branch around the periphery of the gland before penetration. This feature can give a characteristic arc or rim of vascularity. The overlying thyroid gland may also show an area of asymmetric hypervascularity that may help to locate an underlying adenoma.



    Nuclear medicine

    Can be very useful for localising the lesion when the site is not known. Shows increased uptake with agents such as Technetium (Tc) 99m Sestamibi (MIBI) (commonly used agent) and Tc-99m tetrofosmin. The nuclear medicine scan can be fused with the CT scan as a SPECT scan increase diagnostic accuracy.



    CT

    CT is more commonly used in the setting of a failed parathyroidectomy for the detection of suspected ectopic-often mediastinal-glands 6. CT may be also be more helpful for smaller adenomas in the setting of prior negative parathyroid scintigraphy 5.

    Parathyroid adenomas can demonstrate intense enhancement with contrast. This enhancement tends to be early 7.



    MRI

    There can be variable signal intensity on MRI.

    Reported signal characterisitcs include

    • T1 -

    o typically intermediate to low signal

    o subacute haemorrhage can cause high signal intensity 6.

    o fibrosis or old haemorrhage can cause low signal intensity 6

    • T2 -

    o typically hyperintense

    o subacute haemorrhage can cause high signal intensity 6.

    o fibrosis or old haemorrhage can cause low signal intensity 6

    Due to most lesions demonstrate high T2 signal intensity, the addition of contrast for MR scanning does not significantly increase detection.



    Differential diagnosis

    For a non ectopic (eutopic) adenoma on ultrasound, consider an eccentric thyroid nodule.





    Source:

    http://radiopaedia.org/articles/parathyroid-adenoma

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