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KEY CONCEPTS
Cutaneous lymphomas are a heterogenous group of B- and T-lymphocyte infiltration to the skin with varying clinical behaviors and prognoses.
Mycosis fungoides (MF) is the most common subtype of cutaneous T-cell lymphoma (CTCL) with typical indolent course, but a subset of patients can progress to more advanced stages involving nodal and blood compartments.
Sézary syndrome (SS) is a leukemic variant of CTCL with a more aggressive course. In many patients, skin biopsy is nondiagnostic because it does not reveal malignant cells, and diagnosis is made by peripheral blood flow cytometry or Sézary cell count.
The treatment of patients with CTCL is guided by stage and distribution of the skin involvement. The initial treatment approach to skin-limited disease is embodied by the use of skin-directed treatment modalities.
Two newly approved treatment options for patients with relapsed refractory MF and SS include brentuximab vedotin and mogamulizumab, which target skin and blood compartments of disease, respectively.
Primary cutaneous B-cell lymphomas should be distinguished from secondary metastasis of B-cell lymphoma to the skin and are typically associated with an indolent disease course and a favorable prognosis.
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Cutaneous lymphoma is an umbrella diagnosis consisting of multiple subtypes involving malignant mature B- or T-lymphocyte infiltration in the skin. It should be distinguished from secondary metastasis of systemic lymphoma to the skin where involvement in the skin is considered advanced stage. Cutaneous T-cell lymphoma (CTCL) is considered a rare entity consisting of approximately 4% of all cases of non-Hodgkin lymphoma.1 In the majority of patients with CTCL, the disease course is typically indolent; however, in a subset of patients, the prognosis is less favorable, and progression to advanced-stage disease with nodal, blood, and visceral compartments can develop. The cutaneous B-cell lymphomas are less common than their T-cell counterparts, also with a favorable prognosis in the majority of patients.2,3
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In 2008, the World Health Organization (WHO) established the classification of cutaneous lymphomas. This classification was updated in 2016 and again by the WHO–European Organization for Research and Treatment of Cancer (EORTC) and provides the basis for subcategorization of this disease (Table 12–1).2 Each subtype carries differing clinical presentation, histopathologic features, prognoses, and treatment approaches. The various subtypes of cutaneous B and T-cell lymphomas can be separated into aggressive and less aggressive forms (Table 12–2). Mycosis fungoides (MF), pagetoid reticulosis, and CD30+ lymphoproliferative disorders are considered relatively indolent diagnoses. For B-cell lymphomas, marginal zone and follicle center cell lymphomas are favorable subtypes. In indolent cutaneous lymphoma, skin lesions can wax and wane for years and sometimes even self-resolve without treatment. In more aggressive subtypes such as Sézary syndrome (SS), primary cutaneous γδ T-cell lymphoma (pcGDL), and primary cutaneous CD8+ epidermotropic cytotoxic T-cell lymphoma, diffuse large-cell lymphoma, eg type (DLBCL leg type), patients characteristically develop rapidly progressive skin lesions and systemic involvement pertaining to a poor prognosis.4,5 It is critical to ...