Endocrine Abstracts

Introduction: Positron emission tomography - computed tomography (PET-CT) is a highly sensitive imaging modality for evaluating a variety of conditions, including detection of cancer and potential metastases. PET-CT positive thyroid lesions are found incidentally in about 2.5 % of the scans. They can be focal or diffuse and as they pose a considerably high risk of malignancy further diagnostic tests such as neck ultrasound and fine-needle aspiration biopsy (FNAB) are recommended.

Objective: To assess the sonographic and cytological characteristics of PET-CT positive thyroid lesions in a single university endocrine center between 2019-2022.

Patients and Methods: The study included 42 patients (35 women and 7 men) who underwent PET-CT for suspected or confirmed non-thyroid malignancy. The patients were referred for further diagnostic evaluation to the endocrinology department of Kaspela University Hospital, Plovdiv, Bulgaria. All patients had clinical examination, neck ultrasound and FNAB with subsequent cytological examination when indicated. The ultrasound findings were described according to EUTIRADS reporting system and the cytological report was consistent with BETHESDA system. Surgically removed thyroid lesions were further evaluated by pathologist.

Results: The ultrasound examination revealed focal lesions determined as nodules in 35 of the studied patients. In the remaining 7 cases no distinct thyroid lesion was identified (EUTIRADS 1) and the presence of autoimmune thyroiditis was confirmed. After FNAB 12 nodules (34.3 %) were determined malignant or suspicious for malignancy and 91.7 % were confirmed histologically as thyroid carcinomas (n =11). All of the malignant nodules had at least one risk ultrasound characteristic (EUTIRADS 5). The distribution of the remaining nodules with regards to the US fundings was as follows: EUTIRADS 4 – 4; EUTIRADS 3 – 13, EUTIRADS 2 – 6. The overall incidence of malignancy among PET-CT positive thyroid nodular lesions in our center was 31.4 %.

Conclusion: The results from the present sample confirm the high frequency of thyroid neoplasms among all the incidental findings in the thyroid gland detected on PET-CT. Careful ultrasound examination followed by FNAB is justified in all patients to avoid overdiagnosis and unnecessary interventions