[T-cell/histiocyte-rich B-cell lymphoma: histology, immunophenotype and differential diagnosis].

OBJECTIVE: To study the histology, immunophenotype and differential diagnosis of T-cell/histiocyte-rich B-cell lymphoma (TCRBCL).

METHODS: A review of 245 cases of so-called Hodgkin lymphoma diagnosed during the period from 1980 to 2000 in 3 hospitals in Guangzhou, 8 cases were reclassified as TCRBCL, according to the 2001 World Health Organization classification of lymphoid neoplasms. An additional 8 cases of TCRBCL were retrieved from consultation files, as well as routine biopsy cases encountered between 2000 and 2004. Immunohistochemical studies were performed on paraffin-embedded tissue by SP technique in order to study the immunophenotype of the large neoplastic cells (CD20, CD79a, CD3, CD45RO, CD15, CD30, CD10, bcl-6 and EMA) and background non-neoplastic cells (CD3, CD8, CD20, CD45RO, CD79a, CD57, CD68, CD21, CD35, cyclin D1, TIA-1). In-situ hybridization for EBER 1/2 and immunoglobulin heavy chain gene rearrangement study were also performed in 4 and 4 cases respectively.

RESULTS: Among the TCRBCL cases studied, there were 8 males and 8 females. The age of patients ranged from 10 to 68 years old (mean = 40.3 years old). All had lymphadenopathy and hepatosplenomegaly. On presentation, 3 cases belonged to stage II, 10 cases stage III and 3 cases stage IV. Histologically, scattered atypical large neoplastic cells were seen in a background of small lymphocytes and sometimes histiocytes. The large cells exhibited CD20+, CD79a+, EMA+, CD15- and CD30- phenotype. On the other hand, the background small lymphocytes were CD3 and CD45RO-positive. Most of these background T cells expressed CD8 and TIA-1, while they were mostly CD57-negative. The histiocytic cells were CD68-positive; and CD21 and CD35-positive follicular dendritic cell meshworks were absent. In-situ hybridization for EBER 1/2 showed negative nuclear signals. Immunoglobulin heavy chain gene rearrangement study revealed clonal pattern in all the 4 cases tested.

CONCLUSIONS: TCRBCL is a rare subtype of lymphoma, with distinctive histology and immunophenotype. The above features are helpful in delineating this entity from Hodgkin lymphoma, reactive lymphoid hyperplasia and lymphomatoid granulomatosis.