Cutaneous pseudolymphomas

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2. DEFINITIONCutaneous pseudolymphoma is defined by theWHOas a reactive polyclonalbenignlymphoproliferativedisease, predominantlycomposed of either B-cells or T-cells, localisedor disseminated. 3. CLINICAL ASPECTS Clinical manifestations are frequently not diagnostic and overlap with lymphoma.Two main problems exist:1. Lesional regression is common in cutaneous lymphoma and accordingly, regression does not necessarily indicate that the lesion is pseudolymphoma.2. Occasionalcasesofinitialcutaneous pseudolymphoma can evolve into lymphoma (so- called pseudo-pseudolymphoma) 4. In general, pseudolymphoma is rare on the scalp and never displays clinical poikiloderma. Inaddition, lesions showing variability in size, shape and colour and occuring in non- exposed skin (such as buttocks) should be regarded as cutaneous T-cell lymphoma (CTCL) until proved otherwise. 5. SPECIFIC DISEASES THAT CANMIMIC CUTANEOUSLYMPHOMA 6. EPITHELIAL NEOPLASMS:Tumours such as neuroendocrine carcinoma(Merkel cell tumour), neuroblastoma andprimitive neuro-ectodermal tumour can mimiccutaneous lymphoma.Epidermal involvement in Merkel cell tumourcan result in intra-epithelial collections ofcells that mimic Pautrier micro-abscesses inCTCL 7. LYMPHOCYTE-RICH EPITHELIAL NEOPLASMSClassically theseincludeeccrinespiradenoma and lympho-epithelioma-likecarcinoma of the skin.A more recent entity is cutaneous lymph-adenoma, although increasingly this isregarded as a trichoblastoma withadamantinoid features 8. CUTANEOUS LYMPHADENOMAThere is outer palisading of cells, focally with clear-cellchange, within a loose fibrous stroma. There is also focal pigmentand a possible papillary mesenchymal body (lower left edge).Numerous intraepithelial lymphocytes are present, characteristic ofthis lesion. 9. IMMUNE RESPONSE TO EPITHELIAL DYSPLASIA OR MALIGNANCY AND OTHER NEOPLASMSCutaneous neoplasms such as basal cellcarcinoma, malignant melanoma anddermatofibroma can elicit extremelystrong lymphocytic stromal responses, inwhich the underlying neoplasm can bedifficult to identify.Lymphomatoidvariantsofactinickeratosis and benign lichenoid keratosis(lichen planus-like keratosis) exist. 10. DISEASES SEENUNCOMMONLY IN THE SKIN Include Extramedullary haemopoiesis, Malakoplakia, Whipples disease Ectopic thymus Rosai-Dorfman disease Inflammatory pseudotumour, Castlemans disease and Kikuchis disease. 11. ROSAI-DORFMAN DISEASE: Can herald, co-exist with or follow nodal orsystemic disease Itshistologicappearance is usefullyremembered by the alternative term ofhistiocytic lymphophagocytic panniculitis. S100 positive Moderate number of plasma cells present andstroma appears sclerotic or storiform. 12. CUTANEOUS ROSAI-DORFMAN DISEASE displaying large atypical histiocytes 13. INFLAMMATORY PSEUDOTUMOURS: A spectrum of disease that incorporatesplasma cell granuloma and inflammatorymyofibroblastic tumour. Former can display germinal centres, plasmacells and fibrosis. Thelatter displaysmyofibroblasticproliferation and 2p23 re-arrangement 14. CASTLEMANS DISEASE: especially the plasma cell variant, can present in the skin and in particular the vulva. The identification of human herpes virus type 8 can be helpful. 15. KIKUCHIS DISEASE: Display the characteristic features of necrosis, karyorrhexis, apoptosis, immu noblasts and plasma cells. Excludepossibility oflupus erythematosus. 16. CLASSICAL DERMATOSES Many classic dermatoses mimic lymphoma and this is particularly frequent with autoimmune and connective tissue disorders.1. Lupus erythematosus2. Lichen sclerosus3. Pigmented purpuric dermatosis and lichen aureus4. Lymphomatoid dermatitis/eczema5. Lymphotoid folliculitis6. Acne rosacea 17. 7.Angiolymphoid hyperplasia and Kimurasdisease8.Chronic photodermatoses9.Perniosis (chilblains)10. Annular erythemas11. Traumatic ulcerative granuloma(eosinophilic ulcer/granuloma of thetongue)12. Jessner and Kanofs lymphocyticinfiltration of the skin 18. LUPUS ERYTHEMATOSUS:(lupus erythematosus panniculitis) Characteristic features include epidermal involvement,germinal centre formation, plasma cells and hyaline necrosis. Cases may be extremely difficult to distinguish from subcutaneous panniculitis-like T-cell lymphoma. 19. This has resulted in some acceptance of an intermediaryentitydescribedas indeterminate lymphocytic lobular panniculitis or atypical lymphocytic lobular panniculitis Lupus erythematosus display localisation on hair follicles mimicking the folliculotropic variant of mycosis fungoides. 20. LICHEN SCLEROSUS: The interface dermatosis present in lichen sclerosus can closely mimic cutaneous CTCL in early stages. Can display florid, small-to-medium blood vessel lymphocytic vasculitis which closely resembles angiocentric variants of cutaneous lymphoma 21. PIGMENTED PURPURIC DERMATOSISAND LICHEN AUREUS Suspicionraised in cases which are persistent or contain atypical cells. Inthese cases, consideration should be given a possible drug-related aetiology. 22. LYMPHOMATOID DERMATITIS/ECZEMA Described in association with external sensitization, it is now recognised to occur in occasional cases of atopic dermatitis and in particular, those with high IgE levels 23. LYMPHOMATOIDFOLLICULITIS Predominantlyin patients under 50 years of age Immunohistochemistry reveals mixed populationsof B- and T-cells. Most characteristic diagnostic feature is thepresence of moderate numbers of perifollicularantigen-presenting cells which are CD1a and S100positive. Anotherfeature is the tendency towardsspontaneous regression. 24. ACNE ROSACEA Characterised by follicular interface changes which, together with a paucity of granulomas, can mimic early stages of follicular CTCL. 25. ANGIOLYMPHOID HYPERPLASIA ANDKIMURAS DISEASE Characterisedbylargenumbersof lymphocytes and / or eosinophilis. Prominenthob-nail endothelial cells with vacuolesinsmall-to medium sized vessels, and germinal centres are the main diagnostic clues to angiolymphoid hyerplasia Kimurasdisease can mimic human T-cell lymphotropic lymphoma. 26. CHRONIC PHOTODERMATOSES Chronicactinic dermatitis (including actinic reticuloid) and polymorphous light eruption are classical mimics of cutaneous lymphoma. Histological clues in chronic actinic dermatitis include dermal fibrosis and multinucleate stromal giant cells Polymorphouslight eruption is often associated with edema of papillary dermis 27. Actinicprurigo recently added to this group and cause diagnostic problems by a high density of B-cells Photodermatoses can display increases in CD8 T-cells but this phenotype can also be present in some variants of CTCL. 28. PERNIOSIS (CHILBLAINS) An abnormal inflammatory response to cold, seen most frequently in acral locations, but it can occur on the thighs of horse-riders. Mimicked by variants oflupus erythematosus termed chilblain lupus. Both perniosis and chilblain lupus can resemble lymphoma because of dense perivascular collections of lymphocytes. 29. ANNULAR ERYTHEMAS Especiallyerythema annulare centrifugum canmimiclymphomawith dense perivascular collection of lymphocytes. 30. TRAUMATIC ULCERATIVE GRANULOMA(EOSINOPHILIC ULCER/GRANULOMA OF THE TONGUE) Located on the tongue, this entity can contain eosinophils and blast cells mimicking lymphoma. 31. JESSNER AND KANOFS LYMPHOCYTICINFILTRATION OF THE SKIN Lesionsare usually on the face and discoid in nature. Papules expand peripherally but clear in centre and give rise to a circinate appearance. Spontaneous remission can occur but remission in weeks, months, or longer. 32. Histologically, mild perivascular and peri- adnexal lymphocytic infiltrate. There should be no involvement of the epidermis and oedema of papillary dermis appears frequent. Immunohistologysuggested increased dermal CD8 lymphocytes but no HLA-DR expression. This contrasts with lupus erythematosus which has fewer CD8 lymphocytes and greater HLA-DR expression. 33. Somestudies highlighted the presence of so- called plasmatoid monocytes. The entity may overlap with polymorphous light eruption or lupus erythematosus. The entity has been described in HIV positive patients and occasionally, as a drug reaction. 34. SPECIFICALLY NAMED CUTANEOUSPSEUDOLYMPHOMAS 35. ACRALPSEUDOLYMPHOMATUS ANGIOKERATOMA OF CHILDREN(APACHE) Firstdescribed in children on the extremities of arms and legs and often multiple and unilateral. Histologically,it is characterised by prominent postcapillary venules and a moderately dense lymphocytic infiltrate. 36. The cellular infiltrate may show interface changeswith the epidermis and immunohistochemistry revealsmixed populations of B- and T-cells There appears to be overlap with the entity of papular angiolymphoid proliferation with epithelioid features (PALEFACE). 37. SOLITARY PSEUDO T-CELL LYMPHOMA Characterised by mixed populations of B- and T- cells, an increase in CD8 T-cells and the presence of histiocytes. Thereappears to be some overlap wit lymphomatoid benign lichenoid keratosis. 38. PSEUDOLYMPHOMAOF HAEMOTOLOGICAL DISEASESyn: insect-bite like reactionor eosinophilic eruption of haematological disease Initiallyrecognized that mosquito bites in patientswith chroniclymphocytic leukemia could be associated with florid cutaneous responses. This was followed by reports of insect bite like reaction in patients with CLL but no apparent history of insect bite. 39. More recently, this pseudolymphotamous reaction has been reported in patients with mantle zone lymphoma and in association with HIV infection. The entity is generally considered to have an association with altered immunity. 40. EXOGENOUSCAUSES OF CUTANEOUSPSEUDOLYMPHOMATUS REACTION 41. DRUGS List of drugs causing pseudolymphomatous reactions is extensive and can be usefully remembered by the prefix (anti-). Antidepressants, anticonvulsants, antihypertensives, antibiotics, anti-inflammatory and antihistamines. To this can be added calcium-channel blockers, lipidlowering drugs,colonystimulatingfactor