Consortium for Improving Survival of Lymphoma (CISL): a model of multicenter collaboration for lymphoma studies in Korea.

Lymphoma is the most common hematologic malignancy, accounting for more than 40% of hematologic malignancies in Korea [1]. However, lymphoma is not a single disorder but a heterogeneous group of subtypes that arise from abnormal B cells or T/NK cells at various stages of development. Although the diagnosis of lymphoma is mainly based on the pathologic findings of lymph node or bone marrow biopsy or both, the number of lymphoma subtypes is expected to increase with advances in molecular and cytogenetic techniques. Besides, the clinical manifestations related to extranodal involvement are also considered for the diagnosis of lymphoma because the involvement of particular extranodal sites can be reflected in the diagnosis of lymphomas. Furthermore, even if patients may have the same subtype of lymphoma, clinical features and treatment outcomes may be different depending on the site involved. Extranodal involvement of lymphomas can be classified as primary or secondary, based on whether the involvement of a certain extranodal organ is a predominant clinical presentation or not. For example, for a case presenting as a lymphoma involving stomach without additional pathologic lesions, it can be designated as primary gastric lymphoma. However, the occurrence of primary extranodal lymphoma is a relatively rare event, especially in those special organs including eyes, thyroid and adrenal glands.

In this issue of the Blood Research, Lee et al. [2] reported the results of nationwide retrospective analysis regarding clinical features and treatment outcomes of 20 patients with intraocular lymphoma in Korea. In the study, they summarized clinical features and treatment outcomes of intraocular lymphoma. The intraocular lymphoma is defined as a lymphoma located inside the eye, which arises from the retina, uvea, or the optic nerve. The clinical data were retrospectively collected from eight hospitals, and the number of cases in this study seems to be sufficient for better understanding of intraocular lymphoma due to extreme rarity of the disease. Given that the majority of physicians may not experience such cases in their clinics, even for hemato-oncologists working in a university hospital, this study would provide useful information to the clinicians as well as the pathologists.

Therefore, multicenter collaborative study is definitely required for this kind of study focusing on rare subtypes of lymphomas or unusual lymphoma cases. The eight hospitals including Dong-A university hospital belongs to the Consortium for Improving Survival of Lymphoma (CISL). The CISL is a study group for prospective clinical trials for lymphoma patients and various retrospective analyses [3]. Since the first meeting in February of 2006, the CISL performed more than 35 prospective clinical trials and comprised of 68 centers under the Korean Society of Hematology Lymphoma Working Party. In addition, the CISL reported many results of retrospective analyses like the article by Lee et al. in Blood Research. The CISL addressed many issues related to primary extranodal lymphomas including those that involved Waldeyer's ring, breast, adrenal and thyroid glands [456789]. The information they reported is expected to provide an evidence for the management of unusual lymphoma cases as well as to help physicians to improve the understanding of those rare extranodal lymphoma cases. Taken together, this report is a good example of multicenter collaborative study for the rare occasions of lymphoid malignancies as well as the outstanding performance of the CISL as a study group for lymphomas. Considering there are many other rare hematologic disorders besides lymphomas, the establishment of study groups for multicenter collaboration should be encouraged more in the field of hematology in the future.