Endocrine Abstracts

Introduction: The number of thyroid cancer diagnosis has increased worldwide. However, its diagnosis, particularly in a case of follicular cancer (FTC), may be challenging. New markers of malignancy are intensively searched for.

Case description: A 29-year-old female was referred for subtotal thyroidectomy in 2006 due to a nodule in the right lobe. The histopathological examination revealed follicular adenoma (FA). During endocrinological follow-up, in 2008 a local recurrence in the thyroid bed and the presence of metastases to the lymph nodes and lungs were observed. Thus, the patient was referred for total thyroidectomy and lymphadenectomy. Histopathological examination of the resected specimen demonstrated the presence of FTC. Due to persistent disease, the patient required two subsequent lymphadenectomies followed by radioiodine therapy. However, the result of the therapy was unsatisfactory. Consultation of the material acquired from the first surgery resulted in conclusion that, taking into account the clinical course of the disease and morphological similarity of weaving in both histopathological specimen, the nodule in the right thyroid lobe operated in 2006 was presumably a FTC. Patient has been subsequently treated by lenvatinib from 2012 to 2015 acquiring total structural and partial biochemical remission. The drug was withdrawn due to the disease recurrence. Patient was reoperated in 2015 and has been treated with sorafenib since 2016. However, the remission of the disease has not been achieved until now. The histopathological specimen from the first surgery has been prepared for next-generation sequencing. DNA was acquired from histopathological slide. NGS sequencing was done on the Ion PGM Sequencer (Thermo Fisher, USA) employing Ion AmpliSeq Comprehensive Cancer Panel. The obtained data from genomic experiments were subjected for analysis using dedicated software. The analysis revealed the presence of fms-related tyrosine kinase 3 (FLT3) mutation on chromosome 13 – c.1683A>G (COSM19740), silent substitution present in coding region, position 561 L→L. The occurrence of the mutation has not been confirmed in the patient’s leucocyte DNA through NGS, which confirms its somatic character.

Conclusions: Although FLT3 has been previously reported in hematological malignancies, such as acute myeloid leukemia or myelodysplastic syndrome, to the best of our knowledge this is the first report of the presence of FLT3 mutation in the thyroid tissue. Due to diagnostic problems in a case of our patient, finding a new marker of FTC and possible prognostic factor is crucial, what might be the basis for new targeted therapeutic options.