Clinicopathological analysis of mediastinal large B-cell lymphoma and classical Hodgkin lymphoma of the mediastinum.

Primary mediastinal (thymic) large B-cell lymphoma (PMLBCL) and nodular sclerosing classical Hodgkin lymphoma (NSCHL) are the major histological types of lymphoma affecting the mediastinum. We reviewed 27 patients with PMLBCL and 14 patients with NSCHL. A poor performance status, high serum lactate dehydrogenase level and strong positivity for PAX5 were all significantly more common in patients with PMLBCL than in those with NSCHL. Severe fibrosis was frequent in NSCHL, but not in PMLBCL. PDL1 was expressed by 11/25 PMLBCLs (44.0%) vs. 1/9 NSCHLs (11.1%). Expression of BCL6 was significantly more frequent in PDL1-positive PMLBCL than in PDL1-negative PMLBCL, but there were no clinical differences between these two groups. Two patients with PMLBCL with a poor prognosis had CD20(-), CD79a(+), CD15(-), and CD30(-), possibly representing a subtype of mediastinal gray zone lymphoma.