The diagnosis of papillary thyroid carcinoma (PTC) is based on nuclear features; however, identification of these features is inconsistent and controversial, and accordingly, the microscopic distinction of PTC from other benign thyroid lesions may be difficult.Aim
The current study was aimed to assess the diagnostic value of HBME-1 and CK19 antibodies in the differentiation of PTCs from their benign mimics and well-differentiated tumors of uncertain malignant potential (WDT-UMP).Methods
The study was conducted on 52 cases of surgically removed thyroid lesions, which were received at Ain Shams University Hospitals during the period from July 2007 to July 2009. The present work comprised 25 cases of PTC, 16 cases of benign thyroid lesions, and 11 cases of WDT-UMP. Paraffin sections from these cases were immunostained for HBME-1 and CK19. After evaluation of both immunohistochemical markers in different studied groups, a protocol was suggested to identify the various degrees of risk potential for malignancy.Results
The results showed that HBME-1 immunoreactivity was positive in 92% of PTC cases compared with 96% of CK19, with the majority of cases showing diffuse strong immunostaining. In the benign thyroid lesions, HBME-1 immunoreactivity was negative in all cases, compared with 68.8% of CK19 cases. HBME-1 showed a higher specificity (100%) and diagnostic accuracy (95%) than CK19, whereas CK19 showed a higher sensitivity (96%). The combined expression of HBME-1 and CK19 enhanced the specificity (69%) and diagnostic accuracy (82.5%) of CK19 markedly. There was a highly statistically significant difference between PTC, WDT-UMP1, and benign thyroid lesions with regard to the distribution of HBME-1 immunoreactivity (P<0.0001). As for CK19 expression, there was a significant difference between PTC and WDT-UMP cases (P<0.05), but no statistical significance between WDT-UMP and benign cases (P>0.05). According to our suggested protocol in evaluating the 11 cases of WDT-UMP, six cases were classified as malignant (54%), one case as suspicious of malignancy (9.1%), two cases as WDT-UMP (borderline) for strict follow-up (18.2%), and two cases as benign (18.2%).Conclusion
HBME-1 attained a higher specificity and CK19 attained a higher sensitivity, which means that the two immunohistochemical markers may be complementary to each other in diagnosing PTC and differentiating it from the benign and borderline lesions.