Endocrine Abstracts

Background: Among differentiated thyroid cancers, follicular thyroid carcinoma (FTC) is the second most prevalent, representing 10-15% of cases. Histopathological features, tumour size, multifocality, presence of lymphnode metastasis at diagnosis are the most impacting features affecting clinical outcome. Tumour microenvironment (TME) may have an important ancillary role for disease progression. We present two cases of FTC with biochemical and structural persistence of disease, with different clinical outcomes and timing of disease progression.

Case report: Case 1 In November 2008, an 81-year-old male underwent total thyroidectomy for a FTC measuring 6 cm with capsular invasion. A 100 mCi radioactive iodine therapy (RAI) was administered. Whole-body scintigraphy (WBS) revealed radioiodine hyperaccumulations in both lung fields, leading to multiple RAI sessions (cumulative dose of 700 mCi). In 2014, after a fourth RAI, WBS highlighted small focal hyperaccumulations in the left lung field. In 2015 at SPECT, a small hyperaccumulation projecting to the liver was observed. In 2021, computed tomography (CT), showed the growth of the hepatic lesion, which was surgically removed. Six months later, multiple subpleural pulmonary nodules were revealed at CT. The patient refused tyrosine kinase inhibitor treatment. Over a 14-year follow-up period, the patient enjoyed a satisfactory quality of life until June 2023 when an uncontrolled disease progression, with bone and cerebral metastasis, led to a fatal outcome. Case 2 In March 2017, a 70-year-old female underwent total thyroidectomy, diagnosed at biopsy as a Hurthle cell carcinoma, followed by 100mCi RAI treatment. In 2018 a thyroid ultrasound identified a cervical anechoic nodule, negative on WBS. Thyroglobulin levels exhibited a consistent increase. A thorax CT scan revealed pulmonary nodules, inactive at WBS. At FDG-PET scan hypercaptation was observable in thyroidal (compatible with residual disease), paratracheal and paraesofageal region. Patient started lenvatinib at low-dose due to poor compliance, systemic adverse effects and low body weight (46 kg). Over a four-year follow-up period, the patient exhibited an unexpected rapid disease progression with a fatal outcome (pulmonary, hepatic and pancreatic metastases).

Conclusions: Patients with FTC may have indolent persistence of disease for several years with an unexpected rapid progression of disease, independent from the histotype and disease extension at diagnosis. These observations suggest a possible role of the TME in influencing the disease outcomes. Future research on the TME complex interactions and its effects on disease outcome, is warranted. This would allow for a more nuanced approach, potentially modulating the TME and improve treatment outcomes.