Non-Hodgkin lymphoma (NHL) is a heterogeneous group of lymphoid neoplasms and the distribution of the NHL subtypes varies across geographic regions [1]. The pattern of NHL in India has been earlier compared with those from other countries [2]. In the current study, we have addressed the following issues with respect to NHLs in children and adolescents: (1) distribution of subtypes of lymphoma in India, (2) distribution of lymphoma subtypes in different age groups (0 -4, 5 -9,10 -14 and 15-19 years), (3) distribution of lymphoma subtypes among males and females, (4) proportion of cases with extranodal presentation among different lymphoma subtypes, and (5) comparison of the pattern seen in this study with those seen in others.
A total of 302 cases in the age group of 0-19 years were analysed. They included cases diagnosed as NHL in the Department of Pathology, Tata Memorial Hospital and in the Lymphoma Registry between January 1995 and June 1998. Only cases where paraffin blocks were available were included in the study. The lymphoma registry was established at the Tata Memorial Hospital in 1994 and it receives cases of lymphoid neoplasms from institutions all over the country [2].
Immunohistochemistry was carried out on paraffin sections in all cases. The cases were reviewed by all three pathologists with two of the pathologists (KNN, CSS) reviewing the slides independently. The cases were classified according to the WHO method [3]. The panel of antibodies used for immunohistochemistry included: (a) monoclonal antibodies to CD15, CD20, CD21, CD30, CD43, CD45, CD45RO, CD68, CD74, CDw75, CD79a, epithelial membrane antigen (EMA), cytokeratin, bcl-2 protein, cyclin D1, kappa light chain, lambda light chain, Ki-B3, Ki-My2P and proliferating cell nuclear antigen (PCNA), and (b) polyclonal antibodies to CD3, Tdt, kappa light chain, lambda light chain and S-100 protein. Immunohistochemistry was performed by the avidin-biotin peroxidase method with pretreatment by heating in a microwave oven in 0.01M citrate buffer pH 6.0/1 mM EDTA buffer pH 8.0 or by proteolytic enzymes-trypsin or pepsin (most of the reagents were procured from DAKO, Denmark).
Thirteen of 302 cases were excluded on review and a diagnosis of NHL was accepted in 289. Those excluded cases included two cases of Hodgkin disease, one of granulocytic sarcoma and ten because of suboptimal quality material. One hundred eighty-three of the 289 cases were cases from the files of the Tata Memorial Hospital. The remaining cases included cases from the Lymphoma registry.
B-cell lymphomas formed 48.1% of NHLs whereas T-cell lymphomas formed 44.3% of all the lymphomas. Classification was not possible in 7.6% cases. The distribution of cases by histologic subtype is shown in Tables I andII. Diffuse large B-cell lymphoma (DLBL) was the most common subtype of B-NHL. B-cell lymphoblastic lymphoma / leukaemia was identified by positivity to CD20/CD79a and Tdt. B-cell lymphomas that could not be subtyped further were assessed for proliferation by proliferation cell nuclear antigen (PCNA) immunostaining and were classified as those with <50% cells (indolent) and those with 50% cells (aggressive) positivity.
Among the T-cell neoplasms, T-cell lymphoblastic lymphoma (T-LL) was the most common subset and positivity for CD3 and Tdt was essential for making