Chapter 66: Cutaneous T-Cell Lymphoma

DEFINITION

• Mycosis fungoides (MF) and its variant Sézary syndrome, the two principal types of cutaneous T-cell lymphoma (CTCL), are malignant proliferations of mature memory T lymphocytes of the phenotype CD4+CD45RO+ (memory T cells), which invariably involve the skin.

• Other types of lymphoma may also have prominent skin involvement (Table 66–1).

EPIDEMIOLOGY

• CTCL is more common in males than females.

• Median age at diagnosis is 55 years.

• In the United States, there are approximately 3000 cases per year, representing about 2% of lymphomas. The annual incidence is approximately 1 per 100,000.

• Americans of African descent have a higher incidence and more progressive disease than Americans of European descent.

• Asians and Hispanics are much less often affected.

• The etiology is unknown.

CLINICAL FINDINGS

• Patients usually present with nonspecific skin lesions (chronic dermatitis) occurring years before diagnosis.

• Early in disease, patients are often diagnosed with eczema (spongiotic dermatitis), psoriatic-like dermatitis, or other nonspecific dermatoses associated with pruritus.

• In early stages of the disease, the lesions may wax and wane.

• Histologic diagnosis may be difficult in early stages. Neoplastic infiltrates may be minimal, masked by normal inflammatory cells, and the neoplastic mature CD4+ phenotype may be misinterpreted as normal inflammatory cells.

• MF may be divided into patch stage (patch-only disease), plaque stage (both patches and plaques), and tumor stage (more than one tumor along with patches and plaques).

• A patch is defined as a flat lesion with varying degrees of erythema with fine scaling; a plaque is defined as a demarcated, erythematous, brownish lesion, with variable scaling of at least 1 mm elevation above the skin surface; and a tumor extends at least 5 mm above the surface (tumors are usually in a setting of patches and plaques) (Figure 66–1).

• Lesions have a predisposition for skin folds and non–sun-exposed areas (bathing-trunk distribution), but in later stages, they can be generalized and involve the face, palms, soles, and other areas.

• Progression through stages usually occurs over years, but some cases ...