Cutaneous Lymphoma

Lymphomas are cancers that arise from lymphocytes, a type of white blood cells with different functions in the immune system. In rare cases, lymphomas can also develop in the skin, where they can arise from both B-, or T-lymphocytes. As such, cutaneous lymphomas are not considered to be skin cancers as they do not arise from normal skin cells.

Cutaneous T-cell lymphoma (CTCL) is the most common type of cutaneous lymphoma, and typically presents with red, scaly patches or plaques on the skin. CTCL often mimics eczema, psoriasis, or other chronic dermatitis, leading to a delayed diagnosis. In general, CTCL follows an indolent disease course (i.e., slowly growing), with only a minority of patients developing advanced disease. The most common type of CTCL consists of Mycosis fungoides (MF). In most patients, MF does not spread beyond the skin. However, in about 10% of cases the disease can progress to lymph nodes and internal organs. Sézary syndrome (SS) is a leukemic form of CTCL and differs from MF by the presence of cancerous lymphocytes in the blood. SS tends to grow and spread faster than MF and is harder to treat. Other CTCL subtypes include primary cutaneous anaplastic large cell lymphoma (pCALCL) and Lymphomatoid Papulosis (LyP).

People with MF, SS or other CTCLs often have a weakened immune systems, which increases their risk for serious infections.

Cutaneous B-cell lymphomas (CBCL) make up about a quarter of all cutaneous lymphomas and arise from B-lymphocytes in the skin. There are 3 main types of CBCL: primary cutaneous follicle center lymphoma, primary cutaneous marginal zone (“MALT”) lymphoma, and the rare primary cutaneous diffuse large B-cell (DLBCL), “leg type” lymphoma. As is the case for CTCL, most CBCLs are slow growing and generally respond well to mild treatments. Of note, several other B-cell lymphomas can also progress into the skin. Given the different way in which primary and secondary skin lymphomas are managed, it is very important to make sure that the lymphoma is truly coming from the skin and not from a systemic lymphoma that has spread to the skin.

In general, skin lymphomas are slightly more common in men than in women and they are usually found in older people. In fact, only about 1 in 5 cutaneous lymphoma patients is younger than 50 years at the time of the diagnosis.

Most cutaneous lymphomas develop slowly, often over many years. As they resemble other skin conditions (e.g., eczema, psoriasis, chronic superficial dermatitis, etc.), the diagnosis for these lymphomas is often delayed.

If a physical examination of the skin lesions is suspicious for a cutaneous lymphoma, a skin biopsy will be taken for further evaluation by a pathologist. In addition to this, blood tests, a bone marrow biopsy or medical imaging tests (PET, CT, MRI, ultrasound) can be performed to assess the spread of the disease.

The treatment for cutaneous lymphoma depends on the type of skin lymphoma and how much of the body is affected by the disease. Given the indolent disease course of cutaneous lymphomas, most patients are diagnosed in an early disease stage. For patients with localized disease (i.e., when the lymphoma is restricted to the skin), skin-directed therapies are preferred. This includes topical creams (often with corticosteroids), light therapy and radiotherapy for thicker plaques, or tumoral lesions.

If these skin-directed therapies don’t lead to a marked improvement, systemic therapies can be used. This may consist of interferon, retinoids (e.g., bexarotene), chemotherapy (often with methotrexate, or gemcitabine), an antibody-drug conjugate (brentuximab vedotin), or a monoclonal antibody (e.g., mogamulizumab). To facilitate an optimal control of the cutaneous lymphoma, systemic and skin-directed therapies are often combined. In this respect, a close co-operation between the dermatologist and the hematologist is warranted.