Primary cutaneous follicle centre lymphoma

PCFCL; Crosti reticulohistiocytoma of the back; primary cutaneous follicular lymphoma

PCFCL is the commonest primary cutaneous B-cell lymphoma in Europe, accounting for roughly half of cutaneous B-cell lymphomas. It is an indolent neoplasm of follicle-centre B cells presenting as solitary or clustered red-violaceous papules, plaques or nodules — most often on the scalp, forehead or trunk. Despite an occasionally alarming clinical appearance, 5-year disease-specific survival exceeds 95%. UK practice favours localised radiotherapy or surgical excision for localised disease and rituximab monotherapy for multifocal or recurrent disease. Systemic follicular lymphoma involving the skin (which behaves more aggressively) must be excluded by staging.

CurrentLast reviewed 15 May 2026

Clinical features

Solitary or clustered red-violaceous papules, plaques or nodules, often firm and rubbery.
Preferential sites — scalp, forehead, neck, upper trunk; trunk-localised disease on the back is known as Crosti reticulohistiocytoma.
Median age 50–60; slight male predominance.
Slow growth over months; ulceration uncommon.
Lower-limb involvement is rare and should prompt consideration of leg-type DLBCL.

Histology and immunophenotype

Nodular or diffuse infiltrate of centrocytes and centroblasts in the dermis, sparing the epidermis (Grenz zone).
Immunophenotype — CD20+, CD79a+, BCL6+, CD10 variable, BCL2 typically negative or weak, MUM1 negative.
Ki-67 generally low.
t(14;18) BCL2/IgH translocation usually absent — distinguishes PCFCL from nodal follicular lymphoma involving the skin (where BCL2 is strong and t(14;18) typically present).
Clonal IgH gene rearrangement in most cases.

Staging and workup

ISCL-EORTC TNM staging for cutaneous lymphomas (separate from MF TNMB).
Baseline — full skin examination, lymph-node examination, FBC, LDH, β2-microglobulin, hepatitis serology (pre-rituximab), CT NCAP to exclude systemic disease, bone-marrow biopsy in selected cases.
If staging reveals systemic disease the diagnosis is reclassified as nodal follicular lymphoma with cutaneous involvement and follows haematological pathways.

Differential diagnosis

Primary cutaneous marginal zone lymphoma — more often on the arms/trunk; small B cells with lymphoplasmacytoid differentiation.
Leg-type DLBCL — aggressive, leg, elderly, BCL2+/MUM1+.
Cutaneous pseudolymphoma — reactive infiltrate without clonality.
Nodal follicular lymphoma involving the skin — BCL2+ with t(14;18).
Cutaneous sarcoidosis, granuloma faciale, Jessner lymphocytic infiltrate.

Management

Localised disease (single lesion or limited cluster) — localised radiotherapy 24–30 Gy in 12–15 fractions OR surgical excision. Complete response rates 95–99%.
Multifocal disease — rituximab monotherapy (375 mg/m² weekly × 4); intralesional rituximab in selected cases.
Relapsed disease — repeat radiotherapy, repeat rituximab; combination chemoimmunotherapy reserved for refractory disease (rare).
Observation is appropriate for asymptomatic minimally progressive disease.

Prognosis and follow-up

5-year disease-specific survival > 95%.
Local cutaneous recurrence occurs in 20–30%, often years later, and does not worsen prognosis.
Follow-up — typically annual review with skin examination and bloods; imaging only if clinical concern.

References

Senff NJ et al. European Organization for Research and Treatment of Cancer and International Society for Cutaneous Lymphoma consensus recommendations for the management of cutaneous B-cell lymphomas. Blood; 2008;112:1600–9.

Willemze R et al. WHO-EORTC classification update. Blood; 2019;133:1703–14.

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.

WHO Classification of Haematolymphoid Tumours Editorial Board. WHO Classification of Haematolymphoid Tumours. 5th ed. Lyon: IARC; 2022.