461 A clinically applicable molecular classification of oncocytic cell thyroid nodules 11 Figure 6A. Molecular alterations observed in 30 oncocytic cell nodules based on CNA-LOH analysis using the GWLOH v2 panel, and somatic point mutation and gene fusion analysis. Nodules 12 and 13 are a left- and right-sided nodule in the same patient. Although CNA patterns appear similar in both nodules, further analysis of the SNP profiles demonstrated that the GH type alterations appeared in different alleles on chromosomes 13 and 22 of the two nodules. The lesions were therefore considered of different clonal origin and both included in the current study. Figure 6B. Clustered bar chart showing the statistically significantly different rate of the CNA patterns among the different histopathological diagnoses (p<0.001). CNA, copy number alterations. GH type, genome haploidization type. GWLOH, genome-wide loss of heterozygosity. OA, oncocytic thyroid adenoma. mi-OCA, minimally invasive oncocytic thyroid carcinoma. NH-H, nodular hyperplasia with oncocytic cell metaplasia. RCI type, reciprocal chromosomal imbalance type. Wi-OCA, widely invasive oncocytic thyroid carcinoma. LOH analysis using the GWLOH panel was performed on the biopsy of the pulmonary metastasis and on preserved FFPE material of the primary tumour. The primary tumour showed extensive GH type CNA with high suspicion of endoreduplication, involving chromosomes 1-4, 6, 8, 9, 11, 14, 15, 20-22 (Figure 1B), also denoting the malignant nature of the lesion. No point mutations or gene fusions were found. A similar CNA pattern was observed in the pulmonary metastasis, confirming its origin. No contralateral thyroid tumour was present. The patient recently underwent completion thyroidectomy and adjuvant radioiodine therapy. Case 16 (Table 2) was a 63-year-old female patient, who presented with a palpable, left-sided thyroid nodule from which Bethesda IV cytology was obtained. She underwent a diagnostic hemithyroidectomy, revealing a 20-mm OCN with a thick capsule and without signs of vascular invasion. On histopathological assessment, the tumour capsule showed a focal interruption of
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