Étude du contenu en ADN nucléaire dans les nodules thyroïdiens

Preoperative Evaluation of Thyroid Epithelial Lesions by DNA Ploidy and Galectin-3 Expression in FNAC

AIM: This study aimed to investigate the value of DNA ploidy and galectins-3 immunostain in the preoperative evaluation of thyroid epithelial lesions.MATERIAL AND METHODS: Sixty patients presenting with thyroid enlargement were included in this study and referred by clinicians for FNA. Routine cytological evaluation was done on PAP   stained slides according to the WHO criteria and at least three slides were prepared for routine cytological examinations. The nuclear DNA analysis was performed at the Pathology Department, National Research Center using the Leica Qwin 500 Image Analyzer (LEICA Imaging Systems Ltd, Cambridge, England). Galectin-3 expression was investigated in all tissues using streptavidin-biotin technique.RESULTS: Conventional Fine needle aspiration cytology (FNAC) of 60 cases could diagnose malignancy with a sensitivity of 60%, negative predictive value (NPV) 71.4%, and overall diagnostic accuracy of 80%. The aneuploidy was significantly associated with malignancy, with sensitivity 90.9%, specificity 83.3% and accuracy 88.3%. On using galectin-3 immunocytochemichal stain on cell blocks prepared from FNA the values were improved, sensitivity 93.3% specificity 86.7% and overall accuracy 90% and it was noticed that galectin-3 over expression was significantly associated with malignancy.CONCLUSIONS: From the results of this study we can consider that DNA ploidy and Galectin-3 could refine the FNA results and  increase its sensitivity as a screening test from sensitivity(60%) to reach sensitivity (93.3%), thus decreasing the false negative cases. From this study, it is concluded that the application of ancillary techniques as galectin-3 immunocytochemical markers may become a reliable indicator for surgical intervention, DNA ploidy measurements on the other hand may be of value in galectin-3 negative cases to determine the behavior of the lesion in such cases & refine the preoperative assessment by out ruling false negative cases.

Genomic differences in benign and malignant follicular thyroid tumours using 1-Mb array-comparative genomic hybridisation

Currently there is a lack of objective markers that can reliably differentiate benign and malignant follicular thyroid tumours. Such markers are needed to avoid the morbidity and cost of diagnosing these lesions by a thyroid lobectomy and then a second operation to remove the remaining half of thyroid if cancer is found. The aim of this research was to look for genomic markers that might solve this important problem. Ethical approval for the project was obtained. DNA was extracted from formalin-fixed paraffin-embedded specimens and copy number analysed using an in-house produced 1-megabase genomic array by comparative genomic hybridization (1Mb-aCGH). Acceptable quality data were obtained in 25/26 (96 %) of adenomas and 17/28 (61 %) of carcinomas. Among the carcinomas, 11 were minimally invasive (MI), 5 widely invasive (WI) and there was one metastasis. Recurrent copy number changes distinguishing benign and malignant included +1p34.2-36.33, +1q, +13q12.11-14.3, +14q22.1-32.33, +20q and -22. +20q became more sensitive (36.4 %) for MI carcinomas, whereas +13q12.11-14.3 and +14q22.1-32.33 became more sensitive (66.7 %) for identifying WI cancers from adenomas. Only in the context of aneuploidy (3 adenomas, 3 MI, 3 WI) there were some specific copy number changes that could differentiate all aneuploid adenomas from carcinomas. This research is the first using 1Mb-aCGH to study benign and malignant follicular thyroid tumours. Overall, the incidence of any copy number changes is low, but there are a number of changes associated with different tumour types. Further research with a larger sample and better quality DNA will clarify these findings.