Aims: To describe the features of a series of nine cases of diffuse large B-cell lymphoma (DLBCL) showing morphological and immunophenotypic features that are intermediate with Hodgkin's lymphoma (HL).
Methods and results: Most cases (6/9) presented as mediastinal tumours affecting young males, while the other three cases arose in extramediastinal locations. Histopathologically, tumours showed diffuse large cell areas in a polymorphous background, with pleomorphic cytology and the common presence of Hodgkin's and Reed-Sternberg cells. Immunophenotypically, tumours shared features of DLBCL and classical HL, with expression of CD30, CD15 (6/9), and a full B-cell profile including CD45RB, CD20, CD79a and OCT2. Epstein-Barr virus-latent membrane protein expression was found in 2/9 cases. The majority of tumours had immunohistochemical features consistent with activation of the NF-(kappa)B pathway, including nuclear location of the c-REL/p65 subunit, overexpression of phosphorylated I(kappa)B(alpha), and overexpression of NF-(kappa)B targets. Finally, 2/9 cases showed 3q27 (BCL6) rearrangement, and 1/9 had p53 gene mutations, both of which are rarely detected in classical HL.
Conclusions: These findings suggest that DLBCLs with HL features constitute a distinctive subgroup of aggressive lymphomas whose neoplastic growth and peculiar characteristics could be facilitated by a particular microenvironment found in the mediastinum.