JSH practical guidelines for hematological malignancies, 2018: 7. Peripheral T-cell lymphoma (PTCL)

Abstract

The 2017 WHO Classification lists approximately 30 disease entities under the category of peripheral T-cell lymphomas (PTCLs) and natural killer (NK) cell neoplasms [1]. The entity-specific prevalence is known to differ between world regions. The International T-Cell Lymphoma Project, a global retrospective study of approximately 1300 patients, found that the most prevalent PTCL entities in western countries, from highest to lowest prevalence, were PTCL not otherwise specified (PTCL-NOS), angioimmunoblastic T-cell lymphoma (AITL), ALK-positive anaplastic large cell lymphoma (ALCL), and ALK-negative ALCL [2]. This chapter covers these four entities. Two other PTCL entities common in Japan, adult T-cell leukemia–lymphoma (ATL) and extranodal NK/T-cell lymphoma, nasal type (ENKL), will be covered in another chapter. Cutaneous T-cell lymphoma (CTCL) is covered in a separate set of guidelines (Evidence-based Guidelines for the Treatment of Malignant Skin Tumors, 2nd Edition) [3]. PTCL, like other non-Hodgkin lymphomas, is staged using the Lugano classification (2014) [4]. The International Prognostic Index (IPI) is a useful prognostic model [2], and an Italian research group proposed the Prognostic Index for PTCL-U (PIT) as an entity-specific prognostic model for PTCL-NOS. The PIT consists of four unfavorable prognostic factors: age > 60 years, performance status (PS) > 1, serum LDH level > institutional upper limit of normal, and bone marrow involvement [5]. The Lugano classification (2014) also includes response criteria for PTCL that incorporates positron-emission tomography findings [4]. Note: rare PTCL entities accounting for less than 5% of all T/NK-cell neoplasms in the International T-Cell Lymphoma Project include enteropathy-associated T-cell lymphoma (EATL), hepatosplenic T-cell lymphoma (HSTL), primary cutaneous ALCL, and subcutaneous panniculitislike T-cell lymphoma [2]. EATL accounts for 9.1% of all lymphomas in Europe, where celiac disease is prevalent, and for 5.8% in North America, but is uncommon in Asia at only 1.9% [6]. In the 2017 WHO Classification, EATL unrelated to celiac disease, which was previously referred to as EATL type II, was moved to a separate category as monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) [1]. HSTL, a neoplasm derived from cytotoxic T cells, typically γδ T cells, is common in young men and is characterized by marked hepatosplenomegaly [1]. Both EATL and HSTL have a poor prognosis when treated with the CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) and CHOP-like regimens, and specific treatments have not been established for these entities. The other two entities are lymphomas that primarily involve the skin and subcutaneous tissue.