Pyramidal Lobe Percentage in Thyroid Gland
The pyramidal lobe is present in approximately 44-61% of individuals undergoing thyroid surgery, representing a normal anatomical component of the thyroid gland that varies in frequency based on detection method and population studied. 1, 2
Incidence Data from Surgical Studies
The frequency of pyramidal lobe identification varies significantly across different studies and populations:
- Prospective surgical series report 61% incidence when actively explored during thyroid operations 1
- Nigerian population study found 44% incidence among patients undergoing total thyroidectomy 2
- Italian surgical series identified 12% intraoperatively, though this lower rate likely reflects detection methodology rather than true absence 3
- Literature ranges from 15-75% depending on whether data comes from autopsy studies, radiologic imaging, or surgical exploration 3
Anatomical Characteristics
The pyramidal lobe demonstrates consistent anatomical patterns:
- Originates from the midline in approximately 50% of cases, with left-sided origin (49-96%) being more common than right-sided (4-10%) 1, 3, 2
- Length ranges from 5-80 mm, with median length of 20-50 mm depending on pathology 1, 2
- More frequently identified in women (62%) than men (50%) 1
- More common in patients under 50 years (67%) compared to those over 50 (54%) 1
Clinical Significance for Surgical Practice
The pyramidal lobe has important implications for thyroid surgery outcomes:
- Always pathologically involved in diffuse thyroid diseases and significantly longer in these conditions 1
- Present in 62% of multinodular goiters but only 4% of malignant thyroid tumors 2
- Incomplete removal can result in disease recurrence in the remaining pyramidal lobe tissue, particularly problematic for autoimmune or malignant disease 4, 5
- Can nullify radioactive iodine therapy benefit if left behind, as it will absorb most of the radioactive material 3
Detection Limitations
Preoperative imaging has significant limitations in identifying the pyramidal lobe:
- Ultrasound identifies only 50% of pyramidal lobes present at surgery, with 4% false positive rate 3
- Tc-99m pertechnetate scintigraphy has 8% false positive rate and variable sensitivity depending on thyroid pathology 3
- No gold standard preoperative diagnostic method exists for pyramidal lobe identification 3
Surgical Recommendation
The pyramidal lobe should be actively explored and mandatorily removed during total and subtotal thyroidectomies, as it represents a normal component of the thyroid gland that can harbor pathology and cause incomplete resection if overlooked 1, 5, 3. The entire anterior cervical region requires careful investigation during thyroidectomy to avoid missing long, thin, or ectopically located pyramidal lobes 3.