B-Cell Lymphomas of the Skin

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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].

^* Includes cases previously designated as primary cutaneous immunocytoma and primary cutaneous plasmacytoma.

NOS, not otherwise specified.

• Primary cutaneous marginal zone B-cell lymphoma (PCMZL) and primary cutaneous follicle center lymphoma (PCFCL) are indolent lymphomas with 5-year survival rates of ≥95% (Table 97.3).

• Diffuse large B-cell lymphoma, leg type (DLBCLLT) and diffuse large B-cell lymphoma, other (DLBCLO) are in a group with intermediate clinical behavior, worse 5-year survival estimates, and require more aggressive treatment (see Table 97.3).

• An approach to the patient with a suspected diagnosis of cutaneous B-cell lymphoma is shown in Fig. 97.1.

Fig. 97.1 Evaluation of the patient with a suspected diagnosis of cutaneous B-cell lymphoma. Algorithm outlining approach to the patient. Courtesy, Lorenzo Cerroni, MD.

Fig. 97.2 Cutaneous marginal zone B-cell lymphoma. A Two well-circumscribed, erythematous nodules on the shoulder. B Dome-shaped erythematous nodule with smooth surface. The surrounding area shows features of acrodermatitis chronica atrophicans. This tumor, which demonstrated prominent lymphoplasmacytic differentiation histopathologically, was classified as a cutaneous immunocytoma in the past. A, B, Courtesy, Lorenzo Cerroni, MD.

Fig. 97.3 Pattern of immunoglobulin light chain expression.

Fig. 97.4 Cutaneous follicle center lymphoma. A Large ulcerated tumors on the scalp surrounded by infiltrated erythematous nodules and plaques. B Large ulcerated tumor on the back. Note surrounding erythematous papules, patches, and plaques (Crosti’s lymphoma). A, B, Courtesy, Lorenzo Cerroni, MD.

Fig. 97.5 Cutaneous diffuse large B-cell lymphoma, leg type. A, B Multiple red-brown papulonodules and tumors on the lower leg. A, B, Courtesy, Lorenzo Cerroni, MD.

Plasma Cell Dyscrasias, Including Multiple Myeloma

For further information see Ch. 119. From Dermatology, Third Edition.

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