Cutaneous T-cell lymphoma (mycosis fungoides):

This is a rare type of skin tumour which often follows a relatively benign course. It presents insidiously with scaly patches and plaques which can look eczematous or psoriasiform. Lesions often appear initially on the buttocks. These lesions may come and go or remain persistent over many years. Patients may well die of unrelated causes. Skin biopsy confirms the diagnosis, showing invasion by atypical lymphocytes. T-cell receptor gene rearrangement studies show that the there is often a monoclonal expansion of lymphocytes in the skin.
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Occasionally the disease can progress to a cutaneous nodular or tumour stage which may be accompanied by systemic organ involvement. In elderly males the disease may progress rarely to an erythrodermic variant accompanied by lymphadenopathy and peripheral blood involvement ('Sézary syndrome').
All patients should be staged at the time of diagnosis to assess for any systemic involvement.
Treatment
Early cutaneous disease can be left untreated or treated with topical steroids or PUVA. More advanced disease of the skin, or systemic involvement, may require radiotherapy, chemotherapy, immunotherapy or electron beam therapy. Bexarotene, an agonist at the retinoid X receptor, can cause regression.
Kaposi's sarcoma
This is a tumour of vascular and lymphatic endothelium that presents as purplish nodules and plaques. There are three types:
The 'classic' or 'sporadic' form (as described by Kaposi) occurs in elderly males, especially Jews from Eastern Europe. It presents as slow-growing purple tumours in the foot and lower leg which rarely cause any significant problem.
The 'endemic' form occurs in males from central Africa and shows more widespread cutaneous involvement as well as lymph node (or occasionally systemic) involvement. Oedema is a prominent feature.
The immunosuppression-related form is more severe and is most common in homosexual patients with HIV (p. 142). Lesions are widespread and often affect the skin, bowel, oral cavity and lungs.
All three types have a strong association with herpes virus type 8 but other factors must be involved as herpes type 8 seroprevalence in the general population is up to 10% in the USA and 50% in some African countries. HAART (p. 143) has significantly reduced the incidence of Kaposi's sarcoma in HIV.
Treatment
Treatment of advanced Kaposi's sarcoma is with radiotherapy, immunotherapy or chemotherapy.