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Author: Vanessa Ngan, Staff Writer, 2006.
Lymphomas are tumours of the lymph nodes and lymphatic system. Extranodal lymphomas are tumours that occur in organs or tissues outside of the lymphatic system. When lymphomas occur in the skin with no evidence of disease anywhere else at the time of diagnosis, they are called ‘primary’ cutaneous lymphomas. There are many different types of primary cutaneous lymphomas but they can be broadly divided into two categories, cutaneous T-cell lymphomas and cutaneous B-cell lymphomas. Of all primary cutaneous lymphomas, 65% are of the T-cell type.
Cutaneous T-cell lymphomas (CTCL) refer to a serious but uncommon skin condition in which there is an abnormal neoplastic proliferation of lymphocytes with a ´T´ subtype (thymus-derived). The diagnosis is made by skin biopsy.
Recently the World Health Organisation (WHO) and European Organization for Research and Treatment of Cancer Classification (EORTC) reached a consensus classification for cutaneous lymphomas  and revised by WHO in 2008 . Cutaneous T-cell lymphomas are broken down into the following classifications.
|Indolent (low-grade/slow growing) clinical behaviour||Aggressive clinical behaviour|
Mycosis fungoides is the most common type of CTCL and accounts for almost 50% of all primary cutaneous lymphomas. The second most common group of CTCL is primary cutaneous CD30+ lymphoproliferative disorders.
Mycosis fungoides is a condition in which the skin is infiltrated by patches or lumps composed of white cells called lymphocytes. It is more common in men than women and is very rare in children. Its cause is unknown but in some patients, it is associated with a pre-existing contact allergic dermatitis or infection with a retrovirus.
Mycosis fungoides has an indolent (low-grade) clinical course, which means that it may persist in one stage or over years or sometimes decades, slowly progress to another stage (from patches to thicker plaques and eventually to tumours).
The name mycosis fungoides is historical and confusing: cutaneous T-cell lymphoma has nothing to do with fungal infection.
In patch stage mycosis fungoides, the skin lesions are flat. Most often there are oval or ring-shaped (annular) pink dry patches on covered skin. They may spontaneously disappear, remain the same size, or slowly enlarge. The skin may be atrophic (thinned), and may or may not itch. The patch stage of mycosis fungoides can be difficult to distinguish from psoriasis, discoid eczema or parapsoriasis.
Patch stage mycosis fungoides
Poikiloderma atrophicans vasculare is an unusual variant in which the skin shows areas of thinning, pigmentary change and dilation of the capillaries (telangiectasia).
Poikiloderma vasculare atrophicans
In plaque stage mycosis fungoides, the patches become thickened and may resemble psoriasis. They are usually itchy.
Plaque stage mycosis fungoides
In tumour stage mycosis fungoides, large irregular lumps develop from plaques, or de novo. They may ulcerate. At this stage, spread to other organs is more likely than in earlier stages. The tumour type may transform into a large cell lymphoma.
Tumour stage mycosis fungoides
There are a number of variants and subtypes of mycosis fungoides (MF). Most follow the same clinical and pathological features as mycosis fungoides but some have distinctive features as described below.
|Folliculotropic MF (follicular cell lymphoma)||
|Granulomatous slack skin||
|Mycosis fungoides palmaris et plantaris||
This is the second most common group of CTCL and accounts for about 30% of all CTCL cases. This group includes primary cutaneous anaplastic large cell lymphoma and lymphomatoid papulosis.
|Primary cutaneous anaplastic large cell lymphoma||Lymphomatoid papulosis|
CD30+ lymphoproliferative disorders
Sézary syndrome is the name given when T-cell lymphoma affects the skin of the entire body. The skin is bright red, thickened, dry or scaly and usually very itchy. Examination usually reveals the presence of neoplastic T cells (Sézary cells) in the skin, in enlarged lymph nodes, and in peripheral blood. The prognosis of Sézary syndrome is generally poor with a median survival between 2 and 4 years. Most patients die of opportunistic infections that are due to immunosuppression.
Adult T-cell leukaemia/lymphoma (ATLL), is a serious blood disease in which there are large numbers of circulating atypical cells. It is caused by a retrovirus infection with human T-lymphotropic virus (HTLV I). The condition can be divided into acute and chronic types. Acute ATLL is characterised by skin lesions similar to those found in mycosis fungoides or Sézary syndrome, enlarged lymph glands, high levels of calcium in the blood and bone lesions. Prognosis is poor for this type with survival ranging from 2 weeks to more than 1 year. Chronic ATLL present with skin lesions only and have a longer clinical course and survival, however, this may transform into an acute phase with an aggressive course.
The diagnosis of cutaneous T-cell lymphoma is made clinically and confirmed by a dermatopathologist (see mycosis fungoides pathology). Multiple biopsies are often required to detect the characteristic histopathology changes, especially in the early patch stages. There are characteristic microscopic changes seen on skin biopsy. The diagnosis is often delayed for months or years as early cutaneous T-cell lymphoma can be difficult to tell apart from other skin conditions, particularly eczema.
Enlarged lymph nodes may also be biopsied. Cutaneous T-cell lymphoma can cause harmless swelling, known as ´reactive´ or ´dermopathic´ lymphadenopathy, or result in malignant growth in the lymph nodes.
The blood count is normal in most patients with cutaneous T-cell lymphoma, but an elevated white cell count is characteristic of Sézary syndrome. Some patients may undergo bone marrow aspirate or biopsy.
Patients with advanced cutaneous T-cell lymphoma may have CT or MRI scans to determine whether the disease affects internal organs.
Treatment of individual patients varies and depends on the stage, local expertise and available drugs and equipment. The following may be useful.
Cutaneous T-cell lymphoma may remain confined to the skin for many years, but the abnormal cells may eventually infiltrate other tissues including blood, lymph nodes, lungs, heart, liver, and spleen.
Unlike some other lymphomas, the outlook is generally good. Symptoms can usually be controlled with treatment. However, treatment is not curative.
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