Immunohistochemical typing of non-Hodgkin's lymphoma-comparing working formulation and WHO classification.

The recent WHO classification of non-Hodgkin's lymphoma is based on the morphology and immunohistochemical expression of the lymphoma cells and to a lesser extent, on the molecular and cytogenetic findings. Fifty-three cases of non-Hodgkin's lymphoma were included in the study. Of these, seven cases were primary extra nodal lymphomas. Twenty two patients had peripheral blood and/or bone marrow involvement. A detailed morphological assessment was done and classified using the International working formulation. The two most common types encountered were diffuse large cell lymphoma and small lymphocytic lymphoma. Immunohistochemistry was done using labeled streptavidin-biotin peroxidase complex with CD3, CD20, CD15, CD30, CD 45 (leukocyte common antigen), Cyclin D1, EMA (epithelial membrane antigen). 38 cases (72%) showed B cell expression and 12 cases (22.5%) showed T cell expression. Three cases did not express either marker. B-cell diffuse large cell lymphoma (26%) was found to be the predominant B cell non-Hodgkin's lymphoma. The commonest T-cell lymphoma was T lymphoblastic lymphoma (67%) followed by peripheral T cell angioimmunoblastic lymphoma (25%). Immunohistochemistry is a useful and necessary diagnostic modality and helps subdivide prognostically different types of non-Hodgkin's lymphoma.