MATERIALS AND METHODS: We retrospectively studied CD56 expression in 54 benign and 54 malignant thyroid lesions using archival formalin fixed paraffin-embedded tissue blocks for the study period from January 2010 to December 2015, diagnosed in a tertiary hospital.
RESULTS: CD56 was expressed in 52/54 (96.3%) of benign specimens and only 24/54 (44.4%) of malignant ones. The malignant specimens comprised 31 (57.4%) papillary thyroid carcinomas (PTC), 11 (20.3%) follicular carcinomas (FC), seven (13%) medullary thyroid carcinomas (MC), one (1.9%) poorly differentiated carcinoma (PC) and four (7.4%) anaplastic carcinomas (AC). CD56 was not expressed in 28/31 (90.3%) of the PTCs, 1/11 (9.1%) FCs, 1/4 (25%) of ACs while all MCs and the PD were positive. The benign group comprised nodular hyperplasias (29/54), lymphocytic thyroiditis (10/54), follicular adenomas (FA) (14/54) and one hyalinising trabecular tumour. CD56 was expressed in all the benign cases except one FA and one nodular hyperplasia. Thirteen of the 14 FAs were CD56 positive. The difference in expression between benign and malignant tumours was statistically significant as the p value was <0.01.
CONCLUSION: CD56 is a potentially good immunohistochemical marker for differentiating papillary thyroid carcinoma from other benign follicular lesions of the thyroid especially in differentiating follicular variant PTC from FA in equivocal cases.
MATERIALS AND METHODS: We collected 54 malignant and 65 benign thyroid lesions diagnosed by histology in Universiti Kebangsaan Malaysia Medical Centre between January 2010 and December 2015. All cases were immunohistochemically stained with CK 19 and evaluated by 3 independent observers. The immunostaining patterns were scored based on the intensity and proportion of staining and finally graded as negative, weak positive, moderate positive or strong positive. In addition, the immunostaining scores of the malignant cases were correlated with their TNM pathological tumour stages.
RESULTS: Cytokeratin 19 staining expression was higher in malignant than benign thyroid lesions (p < 0.001) which was most prominent among classical PTC. The four PTC cases that showed negative or weak staining were all follicular variant of PTC. Benign conditions were mostly negative or showed weak positivity. There was no correlation between CK 19 expression and TNM primary tumour stage (pT).
CONCLUSION: Cytokeratin 19 is a useful marker in differentiating malignant from benign thyroid conditions particularly the classical PTC, provided its interpretation is by correlation with morphology and takes into consideration the intensity and proportion of positive staining.