The pyramidal lobe of thyroid is known to carry a high recurrence risk of disease after surgery. To determine the presence of pyramidal lobe before surgery is important. In this study Technetium-99m (Tc-99m) thyroid images were examined to determine the frequency of pyramidal lobe scintigraphic detection. The thyroid scintigrams of 4031 patients (3081 female, 950 male; mean age 43.41±11.06 years, range: 8-85 years) were evaluated retrospectively and classified as chronic thyroiditis, Graves' disease, hypoactive multinodular, hypoactive solitary nodular, active nodular goitre and normal thyroid gland. The frequency of pyramidal lobe in these groups was evaluated. Localization of pyramidal lobe and the relationship between the presence of pyramidal lobe and gender were determined. Pyramidal lobe was positive in 430 patients (10.7%). Of the patients with pyramidal lobe, 76.4% were women and 23.6% were men. The site of origin of the pyramidal lobe was from the right in 43.7%, from the left in 46.7% and from isthmus in 9.5% of the patients. Pyramidal lobe was positive on thyroid images in 20.4%, 11.2%, 14.5%, 2.6%, 0.8% and 10.6% of the patients with Graves' disease, chronic thyroiditis, hipoactive multinodular thyroid disease, hypoactive solitary nodular thyroid disease, active nodular thyroid disease and normal thyroid gland, respectively. The frequency of recurrent thyroid disease involving the pyramidal lobe after surgery highlights the importance of its detection using scintigraphy. Thyroid scintigraphy allows the easy identification of pyramidal lobe. The overall frequency of pyramidal lobe visualization is 10.7%, and its incidence in patients with Graves' disease significantly differes from those of other thyroid pathologies.

Keywords: Pyramidal lobe, thyroid scintigraphy