Cutaneous Lymphoma

What is it?

Cutaneous lymphoma refers to a group of lymphomas (cancers of lymphocytes) that primarily involve the skin. The most common type is mycosis fungoides, a T-cell lymphoma that despite its name has nothing to do with fungal infection. These lymphomas arise when T-cells or B-cells (types of white blood cells) become malignant and accumulate in the skin. Unlike lymphomas that start elsewhere and spread to the skin, primary cutaneous lymphomas begin in the skin and often remain confined there for years, generally having a better prognosis than systemic lymphomas.

Who is affected?

Cutaneous lymphomas are rare but represent the second most common site of extranodal lymphomas.

• Prevalence: Annual incidence of 1 per 100,000 people; mycosis fungoides accounts for 50-70% of all cutaneous lymphomas; approximately 3,000 new cases annually in the United States
• Age distribution: Median age at diagnosis is 55-60 years; can occur at any age including children (rare); incidence increases with age
• Gender: Male predominance with 2:1 ratio for mycosis fungoides; equal distribution for some B-cell subtypes
• Ethnic differences: Mycosis fungoides more common and aggressive in African Americans; presents at younger age in Black patients (median 45 vs 55 years)
• Risk factors: No clear environmental causes identified; possible associations with occupational chemicals, chronic infections; not hereditary but slight familial clustering reported

What causes it?

The exact causes remain unclear but involve immune system dysfunction:

• T-cell lymphomas: Clonal expansion of malignant T-lymphocytes; accumulate in epidermis and dermis; produce inflammatory cytokines causing symptoms; chromosomal abnormalities common but not diagnostic
• Proposed mechanisms: Chronic antigen stimulation theory; viral associations investigated but unproven; occupational exposures (pesticides, solvents) suggested; immune dysregulation and decreased surveillance
• Molecular alterations: Multiple genetic pathways affected; JAK-STAT pathway frequently activated; tumor suppressor genes often deleted; epigenetic changes important
• B-cell lymphomas: Different pathogenesis from T-cell types; some associated with Borrelia infection (Europe); others with viral infections or autoimmune conditions
• Not caused by: Contagious agents - cannot spread person to person; lifestyle factors like diet or stress; sun exposure (actually used as treatment)

What are the clinical features?

Cutaneous lymphoma presentations vary by type and stage:

• Mycosis fungoides - Patch stage: Thin, red, scaly patches resembling eczema or psoriasis; commonly on sun-protected areas (buttocks, breasts, lower trunk); persistent despite topical steroids; may be present for years before diagnosis
• Mycosis fungoides - Plaque stage: Thicker, raised, well-defined red to purple plaques; may be itchy or painful; can develop from patches or appear de novo
• Mycosis fungoides - Tumor stage: Large nodules that may ulcerate; indicates more advanced disease; can appear on previous patches/plaques or normal skin
• Sézary syndrome: Erythroderma (>80% body surface red); severe itching; lymphadenopathy; circulating malignant T-cells in blood; considered leukemic variant of cutaneous T-cell lymphoma
• Primary cutaneous B-cell lymphomas: Solitary or grouped red-purple nodules; three main types with different behaviors; generally better prognosis than T-cell types
• Associated symptoms: Pruritus in 60-80% (can be severe); fatigue and malaise; night sweats and weight loss (advanced disease); frequent skin infections

How is it diagnosed?

Diagnosis requires combination of clinical, histological, and molecular findings:

• Clinical evaluation: Document morphology, distribution, evolution of lesions; photograph for monitoring; assess for systemic symptoms; lymph node and organomegaly examination
• Skin biopsy (essential): Multiple biopsies often needed (30% false negative rate); shows atypical lymphocytes in epidermis (epidermotropism); immunohistochemistry identifies T-cell or B-cell type
• Blood tests: Complete blood count with Sézary cell count; flow cytometry for abnormal T-cell populations; LDH and beta-2 microglobulin (prognostic markers)
• Molecular studies: T-cell receptor gene rearrangement (clonality); helpful but not always positive early; FISH for specific chromosomal abnormalities
• Staging workup: CT or PET/CT for advanced disease; bone marrow biopsy in selected cases; lymph node biopsy if enlarged
• Differential diagnosis: Eczema, psoriasis (early stages); drug reactions; other lymphomas; pseudolymphomas

What treatment options are available?

Treatment is stage-dependent, focusing on skin-directed therapies initially:

• Early stage (IA-IIA) skin-directed therapies: Topical corticosteroids - first-line for patches; topical chemotherapy (nitrogen mustard, carmustine); phototherapy - NB-UVB for patches, PUVA for plaques; total skin electron beam radiation for extensive disease
• Systemic therapies for advanced/refractory disease: Bexarotene (retinoid) - oral or topical; methotrexate, interferon-alpha; histone deacetylase inhibitors (vorinostat, romidepsin); photopheresis for Sézary syndrome
• Novel targeted therapies: Mogamulizumab - anti-CCR4 antibody, FDA approved 2018; brentuximab vedotin - anti-CD30, for CD30+ disease; JAK inhibitors under investigation; CAR-T cell therapy in trials
• B-cell lymphoma treatments: Localized radiation very effective; rituximab for systemic disease; excision for solitary lesions; excellent prognosis for most types
• Supportive care (crucial): Antihistamines and gabapentin for itch; aggressive skin care and emollients; antibacterial washes for infection prevention; psychological support
• Prognosis: Early stage mycosis fungoides - near-normal life expectancy; 10-year survival: Stage IA 95%, IB 85%, IIB 50%, IV 30%; transformation to aggressive lymphoma in 10-20%; most patients die with, not from, early-stage disease

Key points for patients

• Cutaneous lymphoma is usually slow-growing and treatable, especially when caught early
• Many patients live normal lifespans with proper management
• Unlike other cancers, early-stage disease often managed with skin-directed therapies alone
• When to seek medical attention: Persistent rashes not responding to standard treatment; new nodules or tumors developing; severe itching affecting quality of life; constitutional symptoms (fever, weight loss, night sweats)
• Living with cutaneous lymphoma: Regular dermatology follow-ups essential; sun protection (but controlled UV is treatment); maintain good skin hygiene; connect with support groups (Cutaneous Lymphoma Foundation); stay current with evolving treatment options