Chapter 9: T-Cell Lymphomas

PERIPHERAL (MATURE) T-CELL LYMPHOMAS

Peripheral T-cell lymphoma (PTCL) is a heterogeneous group of lymphomas derived from a mature T cell (Fig. 9-1). Currently, the World Health Organization (WHO) classification combines mature T- and natural killer (NK)-cell neoplasms under the umbrella term PTCL, and the category is composed of 23 different entities (Table 9-1), based on the different morphologic, phenotypic, molecular, and clinical features, including disease site (¹). Most PTCLs lack distinct genetic or biologic alterations that are seen in B-cell lymphomas, such as t(14;18) in follicular lymphoma and t(11;14) in mantle cell lymphoma. Compared with B-cell lymphomas, many types of PTCL develop not in lymph nodes, but in specific extranodal sites such as extranodal NK/T-cell lymphoma, nasal type (ENKL) in the nasal cavity, enteropathy-associated T-cell lymphoma (EATL) in the small intestine, and hepatosplenic T-cell lymphoma (HSTL) in the liver and spleen.

EPIDEMIOLOGY

Peripheral T-cell lymphoma represents 5% to 10% of all lymphomas in the United States (²). The most common histologic subtype is PTCL, not otherwise specified (PTCL-NOS), followed by angioimmunoblastic T-cell lymphoma (AITL) or anaplastic large-cell lymphoma (ALCL), either ALK positive or ALK negative. The three types account for about 60% of all cases of PTCLs (³). The age-adjusted incidence in the United States for PTCL-NOS, AITL, and ALCL is 0.30, 0.05, and 0.25 per 100,000 person-years, respectively (²). Previous studies have indicated that some Asian countries have a higher incidence of PTCL (³). However, age-adjusted incidence estimated by population-based ...