ETA2022 Poster Presentations Thyroid Cancer CLINICAL 2 (10 abstracts)
Introduction: Medullary thyroid carcinoma (MTC) is a calcitonin-producing tumor that predominantly occurs in a sporadic form (75%) and less commonly in an inherited form. Besides activating germline mutations of the RET proto-oncogene in hereditary syndromes of MEN2, somatic RET mutations are detectable in about 50% of sporadic MTC. Further, also RAS mutations have been discovered in 30% of RET-negative tumor tissues. Other genetic alterations, chromosomal rearrangements or point mutations in minor genes, are very rare.
Case Report: We report a case of a 38-year-old woman with a nodule in the left lobe, cytologically suspected of MTC. Serum calcitonin was elevated at 217 pmol/l. The patient underwent total thyroidectomy and histopathological examination revealed a 1.3 cm MTC with positive immunohistochemical staining for calcitonin and chromogranin. Molecular genetic analysis detected neither germline RET mutation, nor RET/RAS somatic mutations in examined fresh frozen tumor tissue. A comprehensive NGS panel targeted especially fusion genes, but also other genetic changes, was used for subsequent analysis. Surprisingly, a common V600E BRAF mutation, typical for papillary thyroid carcinoma (PTC), was found. The mutation was confirmed by allele-specific real-time PCR performed from material isolated from both fresh frozen and FFPE tumor tissue. The histological examination demonstrated morphologic features of MTC, no signs of mixed tumor and no evidence of PTC. Interestingly, beside positivity for calcitonin and chromogranin, it showed strong and diffuse CK19 expression, an immunohistochemical marker, typical for diagnosis of PTC.
Conclusions: Only two other cases of BRAF V600E in MTC patients have been reported. In all these studies, the results of molecular genetic analysis were verified by an alternate method, and the tumors were histologically confirmed as pure medullary thyroid carcinomas, without concurrent PTC. The study was supported by projects of the MHCR AZV NU21-01-00448 and MHCRRVO (00023761).
10 Sep 2022 - 13 Sep 2022