The value of CD23 expression as an additional marker in distinguishing mediastinal (thymic) large B-cell lymphoma from Hodgkin lymphoma.

Mediastinal diffuse large B-cell lymphoma (Med-DLBCL) is a subtype of DLBCL that has morphologic and clinical similarities and phenotypic overlaps with classical Hodgkin lymphoma (CHL) involving the mediastinum. CD23 is a marker that has been previously reported in Med-DLBCI and is proposed in the differential diagnosis of M-DLBCL and CHL. A panel of immunostains, including CD45, CD20, CD3, CD30, CD15, CD21, and CD23 as well as Eber was performed on Med-DLBCL and 20CHL. 23/27 Med-DLBCL (85%) were positive for CD23 (membranous) CD30 was negative in 6 and positive in 21 cases. 18 CHL cases were negative for CD23 and only 2 showed rare scattered Reed-Sternberg cells with weak cytoplasmic CD23 staining. CD23 showed a sensitivity of 85% and positive predictive value of 92%. In conclusion CD23 is a useful marker in distinguishing Med-DLBCL and CHL in mediastinal biopsies and may be helpful as an adjunct to histomorphology and other markers in the diagnosis and appropriate clinical management of these lesions.