Endocrine Abstracts

Introduction: Thyroid incidentaloma in 18F-FDG PET-CT is relatively common and the most focal uptake are benign. However, the risk of malignancy of thyroid lesions with focal uptake on 18F-FDG PET-CT is 34.8%. Metastasis to the thyroid is uncommon (less than 0.2% of thyroid fine needle aspiration – FNA - puncture findings), with renal neoplasms being the most frequently associated (48.1%) and, more rarely, those from the breast (7.8%).

Case report: A 54-year-old female with breast adenocarcinoma (HER2+; pT3pN3M0) diagnosed in 2009, underwent neoadjuvant chemotherapy (CT), left radical mastectomy, adjuvant chemoradiation and immunotherapy. Six years later, she had a recurrence of the disease with pericardial effusion. A new CT treatment was performed, and the patient started goserelin, transtuzumab and pertuzumab (dual blockade anti-HER2). In 2020 a 18F-FDG PET-CT was performed and showed mild thyroid uptake in a left lobe’s nodular lesion. At the first Endocrinologist observation she denied cervical compressive symptoms and blood tests revealed euthyroidism. The thyroid ultrasound showed in the left lobe “a nodule with 30x15x25mm, undefined contours, heterogeneous ecostructure, hyperechoic punctate foci … valuable bilateral cervical lymph node expression”. Cytological evaluation of the nodule was suggestive of metastatic carcinoma. Given the absence of possible confirmatory immunohistochemistry (IHC) with FNA and this being the only secondary lesion to suggest progression of the disease, in a multidisciplinary discussion, it was decided to perform total thyroidectomy. The anatomopathological examination clarified the diagnosis, revealing “Thyroid tissue with extensive infiltration by adenocarcinoma. Lymphovascular and neural invasions are identified. The neoplasm coincides with the margin (CK7+, focal GCDFP15, ER 100%, Her2 score 3+, CK20-)”. In this context, she suspended hormone therapy and double anti-HER2 blockade and started CT. She is awaiting for postoperative imaging revaluation.

Conclusion: The report of thyroid focal uptake on PET-CT with 18F-FDG in patients with breast carcinoma should raise the suspicion for metastasis. There is no consensus on the therapeutic approach in these patients, namely with respect to total thyroidectomy. In the present clinical report, histological confirmation with IHC confirmed the progression of the oncological disease and had an impact on the therapy.