Pyramidal lobe of the thyroid
Incidental finding in a patient being investigated for a multinodular thyroid
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Two selected cropped images from a thyroid ultrasound.
The first longitudinal image (labeled CC) shows the pyramidal lobe (open arrows) lying superior to, and contiguous with, the normal isthmus, on the right of the image. Waisting of the thyroid occurs at the junction between the pyramidal lobe and the isthmus.
The transverse image shows the pyramidal lobe in the midline anterior to the trachea with the strap muscles at its lateral aspects.
The pyramidal lobe is a common incidental finding on imaging, especially ultrasound, which is the most common modality employed to assess the thyroid. It is a normal anatomic variant, and a recent large study found it in 21% of a large cohort of consecutive unselected patients attending for thyroid sonography 1.
Unusually in this case the variant lobe was found arising in the midline, which is the rarest position according to the aforementioned study, accounting for only 2% of pyramidal lobes, with approximately equal proportions of the remaining cases arising from the left or the right.