Primary cutaneous diffuse large B-cell lymphoma, leg type
PCDLBCL-LT; DLBCL leg type; cutaneous DLBCL leg type
Primary cutaneous DLBCL, leg type is the aggressive primary cutaneous B-cell lymphoma — characteristically presenting in elderly women (median age ~75) as rapidly growing red-blue tumours on the lower legs, although extra-leg sites occur in roughly 10–15%. Histology shows a confluent diffuse infiltrate of immunoblasts and centroblasts expressing BCL2, MUM1/IRF4 and FOXP1 (non-GCB / activated B-cell phenotype); MYD88 L265P mutation is present in the majority. Five-year disease-specific survival is approximately 50–60%, contrasting sharply with the indolent cutaneous B-cell lymphomas. UK first-line treatment is R-CHOP, with radiotherapy reserved for localised disease in patients unsuitable for chemoimmunotherapy.
Clinical features
- Rapidly growing red-violaceous or red-blue tumours, plaques or nodules.
- Lower-limb predominance (~ 85–90%); upper-limb, trunk and head and neck sites also reported.
- Ulceration in advanced lesions.
- Elderly patients (median 75), female predominance ~ 2:1.
- B-symptoms are uncommon at diagnosis but may emerge with progression.
Histology and immunophenotype
- Confluent diffuse dermal sheets of large B cells — immunoblasts and centroblasts — extending into subcutis.
- Immunophenotype — CD20+, CD79a+, BCL2 strong, MUM1/IRF4+, FOXP1+, CD10 negative.
- Non-GCB / activated B-cell phenotype by Hans algorithm.
- MYD88 L265P mutation in 60–80% of cases — an emerging therapeutic target.
- Ki-67 high (often > 80%).
- Distinguishing from systemic DLBCL with leg skin involvement requires comprehensive staging.
Staging and workup
- ISCL-EORTC TNM staging for cutaneous lymphomas; PCDLBCL-LT is staged T1–T3.
- Baseline — full skin and nodal examination, FBC, LDH, β2-microglobulin, hepatitis B/C and HIV serology, contrast-enhanced CT NCAP, FDG-PET, bone-marrow biopsy.
- Echocardiography prior to anthracycline chemotherapy.
Differential diagnosis
- Systemic DLBCL with skin involvement — exclude by staging; behaviour and management overlap.
- PCFCL with diffuse pattern — BCL2 weak/negative, MUM1-, CD10+.
- PCMZL — small B-cell infiltrate, light-chain restricted plasma cells.
- Intravascular large B-cell lymphoma — intravascular tumour-cell aggregates.
- EBV-positive DLBCL of the elderly.
Management
- First-line — R-CHOP × 6 cycles (rituximab + cyclophosphamide + doxorubicin + vincristine + prednisolone) with intent for cure.
- Localised RT (30–40 Gy) consolidation considered in selected cases.
- Frail/unfit patients — radiotherapy alone or rituximab monotherapy; R-mini-CHOP attenuated regimens.
- Relapsed/refractory disease — second-line chemoimmunotherapy (R-DHAP, R-ICE); autologous stem-cell transplantation in fit younger patients.
- Emerging — Bruton tyrosine kinase inhibitors (ibrutinib) and lenalidomide in MYD88-mutant relapsed disease; CAR-T in highly selected cases.
Prognosis and follow-up
- 5-year disease-specific survival 50–60% — contrasts sharply with indolent cutaneous B-cell lymphomas.
- Adverse features — multiple lesions, lower-limb involvement, ≥ 2 sites, advanced age, raised LDH.
- Follow-up — every 3 months for 2 years, then every 6 months to 5 years; bloods, examination, imaging as indicated.
References
- Willemze R et al. WHO-EORTC classification update. Blood; 2019;133:1703–14.
- Hristov AC et al. Cutaneous lymphomas: 2023 update on diagnosis and treatment. Am J Hematol; 2023.
- Gilson D et al. British Association of Dermatologists and U.K. Cutaneous Lymphoma Group guidelines for the management of primary cutaneous lymphomas 2018. Br J Dermatol; 2019;180:496–526.
- ESMO clinical practice guideline. Diffuse large B-cell lymphoma. Ann Oncol; 2024.
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