Cutaneous T-cell lymphomas, B-cell lymphomas and malignant dermal tumours

Cutaneous T-cell lymphoma (CTCL) is the most common type of skin lymphoma, with an incidence of 0.6 per 100 000 (in the USA). B-cell lymphoma of the skin is rare. Malignant tumours of the dermis are infrequent. The commonest are secondary deposits (p. 109), Kaposi’s sarcoma (p. 71) and a malignancy of dermal fibroblasts (dermatofibrosarcoma).

Cutaneous T-cell lymphoma (mycosis fungoides)

CTCL describes a lymphoma that evolves in the skin, although extracutaneous T-cell tumours often produce secondary skin deposits. CTCL is a slowly progressive tumour of epidermotropic CD3+, CD4+ T lymphocytes that becomes systemic only in its terminal stage.

Clinical presentation

The course is usually protracted, although it is occasionally more rapidly progressive. The diagnosis is often delayed for some years as, in its initial stages, CTCL may resemble eczema or ‘chronic superficial scaly dermatitis’ (p. 56). CTCL can be regarded as having four stages:

1.
Patch stage . Describes small, scaly, slightly raised erythematous patches, typically on the trunk, that can resemble eczema ( Fig. 59.1 ). It may persist for ≥10 years. Occasionally, the skin becomes atrophic, pigmented and telangiectatic (poikiloderma).
2.
Infiltrated plaques . Fixed plaques develop, usually on the trunk but sometimes more widely distributed ( Fig. 59.2 ). This stage may last for years.
3.
Tumour stage . This later phase, characterized by tumorous nodules or ulcers within the plaques, has a 5-year survival of 40%–65% ( Fig. 59.3 ).
4.
Systemic disease . Involvement of lymph nodes or internal organs is a late finding. The Sézary syndrome (p. 58) is a variant.