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.