The role of PCR on diagnosis of small B-cell non-Hodgkin lymphoma

Abstract

Small B-cell non-Hodgkin lymphoma (NHL) is difficult to be distinguished from non-neoplastic reactive process using conventional haematoxylin and eosin (H&E) staining due to different interpretation among pathologists to diagnose based on morphologic features. Ancillary examination such as immunohistochemical (IHC) staining is essential to be conducted. However, a negative or doubtful result is sometimes obtained due to unsatisfying tissue processing or IHC technique. Polymerase chain reaction (PCR) as a molecular diagnostic technique is very sensitive and specific. Clonality detection of heavy chain immunoglobulin (IgH) gene rearrangement has been widely used to establish diagnosis of B-cell NHL. Aims: To elaborate interobserver variation in small B-cell NHL diagnosis based on morphologic features only and to confirm sensitivity and specificity of PCR technique as an ancillary method. Methods: The 28 samples of small B cell NHL and suspicious lymphoma were interpreted by 3 pathologists in Sardjito General Hospital based on their morphology only. The reliability of assessment and the coefficient of interobserver agreement were calculated by Fleiss kappa statistic. Interpretation results were confirmed with IHC staining (CD20, CD3, Bcl2). PCR was performed to analyze the clonality of IgH gene rearrangement. Results: Interobserver agreement in morphologic evalution of small B cell NHL and chronic lymphadenitis revealed kappa coefficient 0.69 included in substantial agreement category. The cases were divided into 3 groups based on morphology and IHC result; lymphoma, reactive process; and undetermined group. PCR analysis showed 90% sensitivity and 60% specificity. Conclusions: The present study reveals a substantial agreement among pathologists on small B-cell NHL diagnosis. On difficult cases, PCR is useful as a complementary method for morphologic and IHC examinations to establish definitive diagnosis.