Primary cutaneous B-cell lymphoma
PCBCL; PCMZL; PCFCL; PCDLBCL leg type
Primary cutaneous B-cell lymphomas (PCBCL) are non-Hodgkin lymphomas confined to the skin at presentation, with no evidence of extracutaneous disease after staging. WHO-HAEM5 / ICC 2022 and the WHO-EORTC cutaneous lymphoma framework recognise three principal entities — primary cutaneous marginal-zone lymphoma (PCMZL), primary cutaneous follicle-centre lymphoma (PCFCL) and primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL leg type). The first two are indolent with excellent disease-specific survival, while leg-type DLBCL behaves aggressively with high mortality. Accurate subtyping by an experienced haematopathologist underpins treatment.
Subtypes
- Primary cutaneous marginal-zone lymphoma (PCMZL) — most common; trunk and arms; multiple violaceous papules and nodules. Indolent. Possible association with Borrelia burgdorferi (more European than UK).
- Primary cutaneous follicle-centre lymphoma (PCFCL) — trunk, head and neck (especially scalp); slowly enlarging plaques and nodules ("Crosti's reticulohistiocytoma" of the back). Indolent.
- Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT) — elderly women; rapidly enlarging red-violaceous nodules / tumours on the lower limb. Aggressive. MYD88 L265P mutation in ~60–80%.
Clinical features
- Indolent (PCMZL/PCFCL): solitary or grouped slow-growing red-pink plaques, papules or nodules; B symptoms absent.
- Aggressive (DLBCL-LT): rapidly growing red-violaceous nodules on shin/calf of an elderly female; ulceration possible; B symptoms uncommon initially.
Diagnosis
- Punch or excisional biopsy with submission of fresh tissue for flow cytometry where feasible.
- Immunohistochemistry: CD20+, CD79a+ B-cell phenotype.
- PCMZL: CD5−, CD10−, CD23−, BCL2+ (variable), monotypic light chain.
- PCFCL: CD10±, BCL6+, BCL2− (typically).
- PCDLBCL-LT: BCL2+, MUM1/IRF4+, FOXP1+; high Ki-67; MYD88 L265P mutation.
- Clonality testing — IGH rearrangement (PCR).
Staging
- CT chest/abdomen/pelvis ± PET-CT to exclude systemic lymphoma (a normal scan is required to define a primary cutaneous lymphoma).
- Bone marrow biopsy in PCDLBCL-LT and selected PCFCL cases.
- Full blood count, LDH, immunoglobulins, hepatitis B/C, HIV serology.
- EORTC TNM staging system for cutaneous lymphoma.
Management
Indolent (PCMZL, PCFCL)
- Localised disease: low-dose involved-field radiotherapy (4 Gy in 2 fractions, or 24–30 Gy) — high response rate, low toxicity.
- Surgical excision for solitary lesions.
- Intralesional rituximab or steroids for selected lesions.
- Watch-and-wait for asymptomatic widespread disease in older patients.
- Systemic rituximab for symptomatic widespread or refractory disease.
Aggressive (PCDLBCL-LT)
- R-CHOP (rituximab + cyclophosphamide + doxorubicin + vincristine + prednisolone) ± involved-field radiotherapy — standard of care.
- Lenalidomide and BTK inhibitors emerging for relapsed/refractory MYD88-mutated disease.
- Manage in collaboration with a haematology MDT.
Prognosis
Indolent subtypes — 5-year disease-specific survival >95%; cutaneous recurrence is common but rarely life-threatening. PCDLBCL-LT — 5-year overall survival 50–60%; better in non-leg disease and after intensive R-CHOP-based therapy. Long-term surveillance for cutaneous and systemic recurrence is required.
References
- Willemze R et al. The 2018 update of the WHO-EORTC classification for primary cutaneous lymphomas. Blood; 2019.
- WHO Classification of Haematolymphoid Tumours, 5th edition (WHO-HAEM5); 2022. International Consensus Classification of Mature Lymphoid Neoplasms; 2022.
- Senff NJ et al. EORTC and ISCL consensus recommendations for the management of cutaneous B-cell lymphomas. Blood; 2008.
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