Hodgkin's Lymphoma (HL) and diffuse large B-cell Lymphoma (DLBCL) are neoplasias derived from B cells that present the same immunophenotypic markers, making the differential diagnosis between them very difficult particularly in cases where morphological overlapping occurs. An extra difficulty exists when the tumor is located in the mediastinum, thereby demanding a more invasive biopsy. In addition, frequently an excessively small sample is collected, putting the analysis of the morphological characteristics of lymphoproliferation at risk. The goal of this study was to evaluate PAX-5 as a marker to distinguish HL from DLBCL. Overall, 10 out of 14 studied cases had a diagnosis of DLBCL and 4 patients of HL. The Pax-5 immunohistochemical staining showed 100% positivity in the LBCL study group. However, 30% showed strong positivity (+++), 50% moderate (++) and 20% weak (+). On the other hand, 50% of the HL group showed a weak focal pattern of staining of the Reed/Sternberg Cells (RSC), whereas the other 50% showed negativity. The weak focal pattern as well as the negative staining pattern of PAX-5 in HL may be an important key in the differential diagnosis as it is very different from DLBCL. Hence, we suggest that the PAX-5 antibody is a good immunomarker and may be used with other markers in the laboratory routine. It is also very useful when associated to clinical features of patients to reach a differential diagnosis between DLBCL and HL mediastinal lymphoma.
Hodgkin's lymphoma; diffuse large B-cell lymphoma; PAX-5 antibody; immunohistochemistry
