Lymphomas and leukaemias
Skin involvement falls into two broad categories:
1 Disorders which arise in the skin or preferentially involve it. These include:
• T-cell lymphoma (mycosis fungoides);
• Sézary syndrome; and
• lymphoma associated with HIV infection.
2 Those arising extracutaneously, but which some-times involve the skin. These include:
• Hodgkin’s disease;
• B-cell lymphoma; and
This lymphoma of skin-associated helper T lympho-cytes usually evolves slowly. There are three clinical phases: the patch, plaque and tumour stages, with involvement of lymph nodes and other tissues occur-ring late in the disease.
The patch stage (formerly termed ‘premycotic’ to denote an early phase of mycosis fungoides) may last for years (see Fig. 6.9). Most commonly it consists of scattered, barely palpable, erythematous, slightly pig-mented, sharply marginated scaly patches rather like psoriasis or seborrhoeic dermatitis. Often they have a bizarre outline (e.g. arciform, or horseshoe-shaped) and, on close inspection, atrophy with surface wrin-kling is usually evident. Their distribution is usually asymmetrical. Less commonly, the patch stage can be a widespread poikiloderma, with atrophy, pigmenta-tion and telangiectasia (Fig. 18.58). As the lymphoma develops, some patches become indurated and pal-pable: the plaque stage. Some then turn into frank tumours which may become large (occasionally like mushrooms, hence the term ‘mycosis fungoides’) and ulcerate (Fig. 18.59).
The patch stage of CTCL may be difficult to diagnose clinically, but the plaque and tumour stages are usually characteristic. The first two phases of the disease may occupy 20 years or more, but the tumour stage is often short, with spread and death usually within 3 years.
The Sézary syndrome is also a CTCL caused by a proliferation of helper T lymphocytes. Generalized skin erythema and oedema is associated with pruritus and lymphadenopathy. Abnormal T lymphocytes, with large convoluted nuclei, are found circulating in the blood (‘Sézary cells’).
The histological hallmarks of plaque stage CTCL are:
• intraepidermal lymphocytic microabscesses (Pautrier microabscesses);
• a band of lymphoid cells in the upper dermis, infiltrating the epidermis; and
• atypical lymphocytes.
The histology of the patch stage poses more problems
and may differ little from dermatitis. Immunopheno-typing and T-cell receptor gene rearrangement studies are not always helpful in reaching a definitive diagnosis. Many biopsies, over several years, may be needed to prove that a suspicious rash is indeed an early stage of CTCL.
The patch and plaque stages may be mistaken for pso-riasis or parapsoriasis , seborrhoeic der-matitis or tinea corporis. However, they respond poorly to treatment for these disorders; the bizarre shapes of the patches and their asymmet-rical distribution often raise suspicion. In the early stages skin scrapings may be needed to exclude tinea.
Moderately potent or potent local steroids, and UVB treatment, may provide prolonged palliation in the patch stage. In the plaque stage, PUVA, oral retinoids and α-interferon are helpful. If lesions become more indurated, electron beam therapy may be used. Top-ical nitrogen mustard paint has also been used with success in both patch and plaque stages. Individual tumours respond well to low-dose radiotherapy. Systemic chemotherapy is disappointing.
This is of interest to dermatologists because it may present with severe generalized pruritus .
Patients with unexplained pruritus must be examined for lymphadenopathy and hepatosplenomegaly. Only rarely does Hodgkin’s disease affect the skin directly, as small nodules and ulcers.
Rarely, the first sign of leukaemia is a leukaemic infiltrate in the skin. Clinically, this shows as plum-coloured plaques or nodules or, less often, a thicken-ing and rugosity of the scalp (cutis verticis gyratum). More often, the rashes associated with leukaemia are non-specific red papules (‘leukaemids’). Other non-specific manifestations include pruritus, herpes zoster, acquired ichthyosis and purpura.
B-lymphocytic lymphomas presenting with skin lesions are rare. They appear as scattered plum-coloured nodules (Fig. 18.60). Histologically, a B-cell lymphoma infiltrates the lower dermis in a nodular or diffuse manner. Immunophenotyping shows a monoclonal expansion of B lymphocytes. Treatment is with radio-therapy and systemic chemotherapy.