Diffuse large B-cell lymphoma of the breast: a distinct entity?

editorial Diffuse large B-cell lymphoma of the breast: a distinct entity? The management of squamous cell carcinoma arising in the lung is markedly different than squamous cell carcinoma of the skin, cervix, or larynx. Likewise, the optimal management of diffuse large B-cell lymphoma sometimes varies by the primary site of involvement. Knowledge of the unique clinical behavior of lymphoma arising in certain extranodal sites is necessary. Examples of this include the requirement for specialized evaluation and treatment of diffuse large B-cell lymphoma arising in the eye, brain, and testicle. It has also been questioned whether primary diffuse large B-cell lymphoma of the breast is another entity that requires management that is different than localized diffuse large B-cell lymphoma that occurs in nodal or other extranodal locations. The report by Ryan et al. [1] from the International Extranodal Lymphoma Study Group (IELSG) in this issue of the journal attempts to answer this question. This analysis adds to the valuable information provided by other studies from the IELSG that have examined non-Hodgkin's lymphomas occurring in other sites [2–4]. Large multi-institutional reviews of this type are designed to eliminate some of the reporting bias in other smaller series of primary breast lymphoma. Nevertheless, patients in this cohort were diagnosed over a 23-year period beginning in 1980 and this analysis is also subject to problems associated with a lack of central pathology review and standardized management. In addition, patients were treated in the 'Pre-PET' (positron emission tomography) and 'Pre-rituximab' era. Despite these limitations, this is the largest series of primary diffuse large B-cell lymphoma of the breast that has been reported and the observations from this study will assist in the management of these patients. The first question addressed is whether the clinical behavior of primary diffuse large B-cell lymphoma of the breast is different than diffuse large B-cell lymphoma arising at other sites. Although the final answer is not known, the propensity for disease to occur and recur in the opposite breast and other extranodal sites indicates that primary diffuse large B-cell lymphoma of the breast has distinct clinicopathological characteristics. As the authors note, a similar situation occurs in testicular lymphoma. Mechanisms of lymphocyte homing to tissues such as skin and gut are well described [5]. Future studies will be required to determine whether specific adhesion molecules, chemokine receptors, or chemokines are involved in the behavior of diffuse large B-cell lymphoma in the …