The Polymerase Chain Reaction in Diagnosis of Small B-Cell Non-Hodgkin Lymphomas.

BACKGROUND

Small B-cell non-Hodgkins lymphoma (NHL) is difficult to be distinguished from non-neoplastic reactive processes using conventional haematoxylin-eosin (HE) staining due to different interpretations among pathologists with diagnosis based on morphologic features. Ancillary examinations such as immunohistochemical (IHC) staining are essential. However, negative or doubtful results are still sometimes obtained due to unsatisfactory tissue processing or IHC technique. The 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 the PCR technique as an ancillary method.

MATERIALS AND METHODS

A toptal of 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 statistics. 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 the substantial agreement category. The cases were divided into 3 groups based on morphology and IHC results; lymphoma, reactive process and undetermined group. PCR analysis showed 90% sensitivity and 60% specificity.

CONCLUSIONS

The present study revealed a substantial agreement among pathologists in small B-cell NHL diagnosis. For difficult cases, PCR is useful as complementary method to morphologic and IHC examinations to establish definitive diagnosis.