DIAGNOSTIC UTILITY OF HBME1 AND CD56 IMMUNOHISTOCHEMISTRY IN DIFFERENTIATING PAPILLARY THYROID CARCINOMA FROM NODULAR COLLOID GOITRE WITH HYPERPLASIA

Abstract

Differentiating papillary thyroid carcinoma (PTC) from nodular colloid goitre with hyperplasia may be difficult when characteristic nuclear features are equivocal. This study evaluated HBME1 and CD56 immunohistochemical expression in PTC and its variants and assessed their diagnostic utility. A retrospective and prospective study was conducted at the Institute of Pathology, Madras Medical College and Rajiv Gandhi Government General Hospital, Chennai, from August 2018 to August 2020. Fifty thyroidectomy specimens were selected, comprising 33 PTCs and variants and 17 nodular colloid goitres with hyperplasia. HBME1 and CD56 were assessed immunohistochemically using predefined scoring systems. HBME1 was positive in 32/33 PTCs (97.0%) and 1/17 nodular hyperplasia cases (5.9%). Its sensitivity, specificity and diagnostic accuracy were 97.0%, 94.1% and 96.0%, respectively. CD56 was negative in 27/33 PTCs (81.8%) and positive in all 17 nodular hyperplasia cases. Its sensitivity, specificity and diagnostic accuracy were 81.8%, 100% and 88.0%, respectively. HBME1 showed moderate or strong positivity in 87% of PTCs. HBME1 demonstrated greater sensitivity, whereas CD56 demonstrated greater specificity for distinguishing PTC from nodular hyperplasia. These findings support the use of HBME1 and CD56 as ancillary immunohistochemical markers in diagnostically difficult thyroid lesions.