457 A clinically applicable molecular classification of oncocytic cell thyroid nodules 11 The histopathological nodule size was similar in benign and malignant nodules (p=0.19), but significantly different between CNA patterns (p=0.02). Post-hoc analysis showed that this difference was based on a larger size in nodules with GH type CNA with suspected endoreduplication than in GH type nodules without endoreduplication (p=0.01). Nodule size was similar between other CNA patterns. Clinical cases Case 23 (Table 2) was a 57-year-old male patient, who was referred to our tertiary care centre with lymphatic, pulmonary, and bilateral renal metastases of an OCA. Twelve years earlier, he had undergone a diagnostic hemithyroidectomy for a right-sided thyroid nodule. At the time, it was morphologically diagnosed as an OA and no further treatment was considered necessary. Recent review of the histopathology slides supported the original morphological diagnosis, showing a 27-mm OCN with large nucleoli, (pseudo-)papillary architecture without papillary nuclear features, and a thin capsule, without signs of capsular or vascular invasion (Figure 7a and 7b). A biopsy of the pulmonary metastasis showed similar histopathological characteristics (Figure 7c and 7d), indicating that, in retrospect, the known OCN should likely be considered an OCA (T2N1bM1). CNATable 1. Baseline characteristics NH-H OA OCA n (patients) n (nodules) 3 3 10 11 16 16 p Female, n (%) 3 (100%) 7 (70%) 8 (50%) 0.21*,** Mean age, years (± SD)§ 55 ± 17 60 ± 12 54 ± 12 0.53†,** Median nodule size on histopathology, mm (IQR) 35 (15-35) 25 (17-40) 38 (21-50) 0.41‡ Bethesda classification 0.80* III - - 1 (6%) IV 3 (100%) 7 (64%) 9 (56%) V - 1 (13%) 2 (13%) not available - 3 (27%) 4 (25%) Molecular testing on cytology 3 (100%) 3 (27%) 6 (37.5%) 0.07* on histopathology 0 (0%) 8 (73%) 10 (62.5%) *: Pearson’s chi-squared test. †: one-way ANOVA. ‡: Kruskall Wallis test. §: mean age at the time of the CNA-LOH analysis. **: calculated on total number of patients. OA, oncocytic thyroid adenoma. OCA, oncocytic thyroid carcinoma. IQR, interquartile range. SD, standard deviation. NH-H, nodular hyperplasia with oncocytic cell metaplasia.
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