Pitfalls in classifying lymphomas.

BACKGROUND

Although the WHO classification (2001) requires a great deal of morphologic, immunophenotypic, genetic, and clinical features for classifying lymphomas, it is still feasible to misdiagnose under limited resources, especially a limited panel of antibodies used for immunophenotyping. To identify pitfalls in classifying lymphomas among hematopathologist, general pathologists, and pathology residents under this situation.

MATERIAL AND METHOD: Newly diagnosed lymphoma cases from 1 July 2002 to 30 June 2003 at Siriraj Hospital were included for two rounds of individually blinded review by a hematopathologist, two general pathologists, and three pathology residents. Final diagnoses were given by consensus. Pitfalls were determined from misdiagnosis, in each case analyzed in terms of frequency.

RESULTS

One hundred and four lymphoma cases included 61 diffuse large B-cell lymphoma (DLBCL, 58.6%), 12 MALT lymphoma (11.5%), eight follicular lymphoma (FL, 7.7%), seven classical Hodgkin lymphoma (HL, 6.7%), four unspecified peripheral T-cell lymphoma (PTCL, 3.8%), three Burkitt lymphoma (BL, 2.9%), two subcutaneous panniculitis-like T-cell lymphoma (SPTCL, 1.9%), and seven other uncommon types (1% each). Pitfalls were low infrequency on diagnosis of DLBCL, nodular sclerosis HL, and SPTCL (8% each), but not different among the participants only in DLBCL. Pitfalls in diagnosis of MALT lymphoma, mixed cellularity HL, BL, unspecified PTCL, and FL were 60%, 50%, 33%, 29%, and 24%, respectively. However, considering hematopathologist and non-hematopathologist groups, pitfalls in the former were lower, especially in the uncommon types of lymphoma.

CONCLUSION

Pitfalls in classifying lymphomas are common. Interest in hematopathology reduces misdiagnosis in lymphomas other than DLBCL.