Diffuse Large B-Cell Lymphoma Arising in Postpneumonectomy Cavities: Report of Two Cases and Literature Review.

Diffuse large B-cell lymphoma (DLBCL) most commonly arises in nodal regions but may also present extranodally. We report two cases of large B-cell lymphoma developing in postpneumonectomy cavities more than a decade after surgery for primary lung carcinoma. In both patients, no history of systemic immunodeficiency, organ transplantation, or chronic immunosuppressive therapy was present, and HIV, hepatitis B, and hepatitis C serologies were negative. In Case 1, the lymphoma showed an activated postgerminal center phenotype and was negative for EBER and HHV-8. In Case 2, the tumor was CD20-negative and EBER-positive, with pathological features of inflammation-associated large B-cell lymphoma. PET-CT was used for staging and response assessment in both patients, and both achieved complete metabolic remission after curative-intent chemotherapy. These cases underscore a rare clinical entity that differs pathophysiologically from pyothorax-associated lymphoma (PAL) or primary effusion lymphoma (PEL). They highlight the postpneumonectomy cavity as a rare but potentially permissive microenvironment for large B-cell lymphomagenesis and underscore the biological heterogeneity of these presentations.