B-Cell Lymphomas of the Skin

97

B-Cell Lymphomas of the Skin

General

• Cutaneous lymphomas can involve the skin as either the exclusive site of involvement (primary cutaneous lymphoma) or as the result of cutaneous involvement in association with a systemic (usually nodal) lymphoma (secondary cutaneous lymphoma).

• Primary cutaneous lymphomas are defined as malignant lymphomas confined to the skin at presentation only after a complete staging evaluation has been performed to exclude a systemic lymphoma.

• Primary cutaneous lymphomas differ significantly from their nodal counterparts in terms of their natural history and thus require a specialized approach to their evaluation and treatment.

• Primary cutaneous lymphomas can originate from B cells (PCBCL), T cells (CTCL), or natural killer (NK) cells.

• Unlike most extranodal lymphomas, T-cell rather than B-cell lymphomas are more prevalent in the skin.

PCBCL

• Primary cutaneous B-cell lymphomas are derived from B lymphocytes in different stages of differentiation.

• B-cell lineage is identified by the presence of CD20 and CD79a and the absence of CD3 markers.

• PCBCLs constitute approximately 20% of all primary cutaneous lymphomas, but there may be regional variation in incidence and specific types of CBCLs.

• Usually affects older adults and males > females.

• Pathogenesis unknown, but in certain areas of the world, Borrelia species are thought to play a role; marked immune suppression/dysregulation is also a risk factor.

• Precise classification can be achieved only after a complete synthesis of clinical, histopathologic, immunophenotypic, and molecular features.

• Once the diagnosis of a B-cell lymphoma in the skin has been made, complete staging (Table 97.1) is recommended to distinguish between primary and secondary cutaneous lymphoma.

• The new World Health Organization–European Organization for Research and Treatment of Cancer (WHO–EORTC) classification provides the basis for a consistent classification of patients and divides PCBCL into four major types (Table 97.2).

Table 97.2

WHO–EORTC 2005 classification of B-cell lymphomas with primary cutaneous manifestations [corresponding entity in the WHO 2008 classification].

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Apr 22, 2016 | Posted by admin in Dermatology | Comments Off

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