Diffuse large B-cell lymphoma occurring in an ovarian cystic teratoma: expanding the spectrum of large B-cell lymphoma associated with chronic inflammation.

Diffuse large B-cell lymphoma associated with chronic inflammation (DLBCL-CI) is a well-recognized entity, originally recorded as pyothorax-associated lymphoma because of the association with artificial pneumothorax. Clinically, it is characterized by a mass arising in a long-standing inflammation and by a poor prognosis. Recently, DLBCL-CI has been described growing along the wall of a preexisting cyst, without forming a mass. Here we describe a case of DLBCL-CI arising in the wall of a mature cystic teratoma of the ovary. On histology, the cystic surface of the cyst was infiltrated by large lymphocytes, immunoreacting with CD20, Multiple Myeloma Oncogene-1/Interferon Regulating Factor-4 (MUM1/IRF4), and PAX5 and positive for Epstein-Barr virus. "Cystic" DLBCL-CIs usually hold an indolent behavior despite heterogeneous therapeutic approaches. Some authors understandably wonder whether patients affected by "cystic" DLBCL-CIs are at risk for overtreatment, and, consequently, DLBCL-CIs associated with cystic lesions should be classified as an entity separated from classic pyothorax-associated lymphomas.