Peripheral T-Cell Lymphoma

Excerpt

Peripheral T cell lymphoma (PTCL) is a heterogeneous group of lymphomas accounting for 5% to 15% of non-Hodgkin lymphomas (NHL), in the western world. It is comprised of peripheral (systemic) and cutaneous forms developed from T-cells and natural killer (NK) cells. Clinically, these lymphomas are often aggressive.

Angioimmunoblastic T cell lymphoma (AITL) is nowadays considered a separate subtype of PTCL. This form, described in 1974 by Frizzera et al., was previously known by several synonyms such as 'angioimmunoblastic lymphadenopathy with dysproteinemia', 'immunoblastic lymphadenopathy', and 'lymphogranulomatosis X'. The follicular T helper cell, based on molecular analyses, is considered the cell of origin for AITL.

Cutaneous lymphomas are NHLs manifesting in the skin in the absence of extracutaneous manifestations at the time of diagnosis. Further subdivided into cutaneous B-cell lymphoma (CBCL) and cutaneous T-cell lymphoma (CTCL), CTCLs comprise up to four-fifths of all primary cutaneous lymphomas. Of note, CTCLs are classified separately from the group of PTCLs.

Among the CTCLs there are Mycosis fungoides (MF), Primary cutaneous anaplastic large cell lymphoma, and Sezary syndrome (SS). MF also termed 'Alibert-Bazin syndrome' or 'granuloma fungoides', represents the most common type of CTCL while remaining a rare type of NHL. Primary cutaneous anaplastic large cell lymphoma is another form of CTCL. Both contribute to roughly four-fifths of all CTCLs.

Large Cell Cutaneous Ki-1 Anaplastic Lymphoma also termed as 'Anaplastic large cell lymphoma' (ALCL) or 'CD30 positive anaplastic large cell lymphoma' is a rare and aggressive type of PTCL (NHL). This form is encompassed among the group of CD30-positive lymphoproliferative disorders and can affect lymph nodes and extranodal sites. Usually, based on the expression of the anaplastic lymphoma kinase (ALK) protein, two sub-types are described: ALK-positive and ALK-negative Large Cell Cutaneous Ki-1 Anaplastic Lymphoma.

SS is a rare leukemic form of CTCL. It is historically identified as a triad of pruritic erythroderma, generalized lymphadenopathy, and the presence of distinct “Sezary cells” in the skin, lymph nodes, and peripheral blood. Although MF is a primary subtype of CTCL, it has historically and inappropriately been used interchangeably with CTCL. It is an aggressive form of CTCL.

This chapter will address:

1. Angioimmunoblastic T cell lymphoma

2. Large Cell Cutaneous Ki-1 Anaplastic Lymphoma

3. Cutaneous T-cell lymphoma:

   1. Mycosis fungoides

   2. Sezary syndrome