Author: Vanessa Ngan, Staff Writer, 2005. Updated by Dr Sara de Menezes, Basic Physician Trainee, Alfred Health, Melbourne, Australia; Chief Editor: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, November 2016.
Lymphomas are tumours of the lymph nodes and lymphatic system.
Primary cutaneous lymphoma can be broadly divided into two categories:
Primary cutaneous B-cell lymphomas (PCBL) comprise approximately 20% of cutaneous lymphomas.
Cutaneous B-cell lymphomas are a malignant proliferation of lymphocytes of the B-cell type. Mutation occurring at different points in B cell development leads to differing forms of lymphoma.
In 2005, the World Health Organization (WHO) and European Organization for Research and Treatment of Cancer Classification (EORTC) reached a consensus classification for cutaneous lymphomas. It was revised by the WHO in 2008. The three main types of PCBCL are:
Rare cases of PCDLBCL that do not belong to the PCDLBCL-LT or PCFCL groups are categorised as PCDLBCL-other. Other entities such as anaplastic or plasmablastic lymphoma, primary cutaneous T-cell/histiocyte-rich B-cell lymphomas and primary cutaneous intravascular large B-cell lymphomas are very rare.
Due to differences in treatment and prognosis, it is important to discern between PCBCL and systemic forms of B-cell lymphomas that manifest with secondary skin involvement.
Especially when involving the head or face, PCFCL can mimic rosacea, folliculitis, acne, lupus miliaris (TB) and insect bites. The list of differential diagnoses should also include basal cell carcinoma, Merkel cell carcinoma, cutaneous lymphoid hyperplasia and other non-B-cell cutaneous tumours (eg, cutaneous T-cell lymphomas).
PCMZL is a low-grade malignant B-cell lymphoma of the MALT (mucosa-associated lymphoid tissue) type.
Often the lesions appear minor clinically, and in some case reports, can mimic the appearance of basal cell carcinoma. Other differential diagnoses include arthropod bites, urticaria, leukaemia cutis and medication-induced pseudolymphoma.
The work-up of PCBCLs should include a complete history, physical and skin examination. Initial blood tests should include:
If the full blood count shows lymphocytosis, peripheral blood flow cytometry may be needed.
An adequate skin biopsy is also important for evaluation and staging. Either 4–6 mm punch, incisional or excisional biopsies should be obtained and should include the reticular dermis and subcutaneous fat. Superficial biopsy specimens may not differentiate PCBCLs from reactive or inflammatory processes.
Assessment for extra-cutaneous involvement should be done, particularly in patients with palpable lymphadenopathy.
Any lymph node identified on imaging > 1.5 cm in length or showing high PET activity should undergo biopsy, excisional biopsy being preferred where possible.
Histologically, PCBCL show a diffuse monotonous population of centroblasts and immunoblasts. Histochemistry tests are essential to classify the exact type of lymphoma.
PCFCL needs to be differentiated from a secondary cutaneous lymphoma, which is where a nodal follicular lymphoma has spread to involve the skin. Cellular morphology may vary with the age and size of the lesion.
Histologically, PCFCL shows:
FISH analysis is unhelpful.
The histology of PCMZL consists of:
PCFCL and PCDLBCL-LT have diffuse large B-cell infiltrates. PCDLBCL-LT shows:
Histopathological differential diagnoses should include:
FISH analysis shows translocations of myc, Bcl-6 and immunoglobulin H genes.
The rarity of PCBCLs and lack of comparative prospective, randomised studies limits the choice of therapy as most treatments are based on data from small retrospective studies. The European Organisation for Research and Treatment of Cancer Cutaneous Lymphoma Group (EORTC-CLG) and the International Society for Cutaneous Lymphoma (ISCL) have uniform recommendations on treating the three main types of PCBCL. Treatment is also influenced by whether the lesion is single or limited to a single site.
Without any treatment, PCFCL lesions may be stable, gradually enlarge, or rarely, regress. The histological growth pattern does not influence survival or treatment choice.
The recommended therapies for PCMZL are similar to PCFCL.
Localised or solitary leg-type B-cell lymphoma is usually are treated with local radiotherapy alone or in conjunction with R-CHOP.
Generalised PCDLBCL-LT can be treated with R-CHOP and/or local radiotherapy. Response rates are high but relapse rates are > 58% Around 30% develop extracutaneous disease.
Trials are assessing the efficacy of biological agents like ofatumumab, lumilixumab, dacetuzumab and intralesional TG1042 in the treatment of PCDLBCL-LT.
Very rarely, PCMZL can transform into DLBCL.
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