[Morphological, morphometrical, and immunophenotypic characteristics of primary mediastinal B-cell lymphosarcoma]

To define histological, cytological, computer-morphometric and immunophenotypical features of primary mediastinal B-cell lymphosarcoma.

The study enrolled 43 patients with primary mediastinal B-cell lymphosarcoma (PMBCL) treated in Hematological Research Center from 1994 to 2002. The examination included morphological and immunophenotypical tests, computer morphometry of the cells by histological sections.

PMBCL is represented by a composite population of cells of a giant, large and small size (nuclear areas 76.24 +/- 19.99, 37.77 +/- 8.0 and 17.12 +/- 4.34 mcm2. Three types were identified: giant-cell, large-cell and small-cell. A giant-cell type is represented by large and giant cells comprising, on the average, 44 and 31% of overall number of lymphoid cells. A large-cell type is primarily represented by large lymphoid cells (62% of the lymphoid population). Small-size type is represented by small cells (72% of cells). Frequent histological signs are diffuse sclerosis and focal necrosis. Tumor cells have B-cell nature. In the giant and large cell type more than 70% cells express PCNA, in the small cell type--less than 30%. Expression of activation marker CD30 is observed in 18% cases in the giant and large cell types.

PMBCL is a morphologically heterogenous disease represented by combination of giant, large and small cells with immunophenotypically B-cell nature characterized in a giant cell and large cell type by prominent but in a small cell and large cell type by insignificant proliferative activity. CD30 expression is observed only in giant cell and large cell types.