Vol 54: april aVril 2008 Canadian Family Physician Le Mdecin de famille canadien 535

Dermacase

Answer to Dermacasecontinued from page 519

3.AtypicalfibroxanthomaAtypicalfibroxanthoma (AFX) isacutaneous tumouroffibrohistiocyticorigin,whichtypicallypresentsasasoli-tary,firm,dome-shapednodule.Itisusuallywelldemar-cated.Thelesiongrowsrapidlybuttendstoremainlessthan2 cm in size.1Ulcerationandminorbleeding canoccur.Thecolourusuallyrangesfrompinktoerythema-tous,althoughapigmentedvarianthasbeendescribedof a brown-bluish colour resulting fromhemosiderindeposition.2Thispigmentedformcaneasilybemistakenformelanoma.

Atypicalfibroxanthomaisprimarilyseeninthehead-and-neck region of the elderly (mean age in the sev-enthdecade).Thenose,cheeks,andearsare themostcommonsitesaffected.3Occurrenceonthescalpmightalso bemore common than previously recognized. Itis possibleAFXmight arise on the trunk and extremi-ties, inwhich case the lesions tend to be larger, lesswelldemarcated,andgrowmoreslowlycomparedwiththose thatappearon theheadandneck.4Thisdistribu-tion,however,isinfrequentandpredominantlyoccursinayoungerpopulationofpatients(meanageinthefourthdecade).3Atypical fibroxanthoma ismost prevalent inthewhitepopulation,andmentendtobeaffectedmorethanwomen.4,5

Themainpredisposing factor is prolongedexposureto sunlight, supported by the fact thatAFX frequentlyappearsonabackgroundofsun-damagedskin.Inaddi-tion,mostpatientshavemultipleactinickeratosesandapast historyof basal cell and squamous cell carcino-mas.5Otherpossiblepredisposing factors includeahis-tory of radiation therapy and local skin trauma.6 TheexactpathogenesisofAFXisnotentirelyunderstood.

DiagnosisEstablishing the diagnosis of AFX based on clinicalgrounds canbe challenging; it is relativelyuncommonandfrequentlyresemblesotherentities.Theclinicaldif-ferential diagnosis includesbasal cell carcinoma, squa-mous cell carcinoma, melanoma, keratoacanthoma,pyogenicgranuloma,andepidermoidcysts.1,5,6Therefore,a skin biopsy is essential inmaking the correct diag-nosis. The histologic differential diagnosis includessquamous cell carcinoma,malignantmelanoma, leio-myosarcoma, and malignant fibrous histiocytoma.5Immunohistochemicalstainingperformedbythepathol-ogisthelpsdifferentiatethesetumours.

TreatmentAtypical fibroxanthoma is considered a low-grademalignancy. It has a relatively benign course and car-riesa favourableprognosiswithappropriate treatment.Metastases (local or distant) are rare and have beenreportedtooccurinapproximately1%ofcases.6

Atypical fibroxanthoma is treated surgically.Widesurgical excisionwith 1-cmmargins used to be thetreatmentof choice; however,Mohsmicrographic sur-geryisnowthepreferredmethod.Mohssurgeryoffers3advantages: lower recurrence rates, tissueconserva-tioninimportantcosmeticareassuchastheheadandneck,andassuranceofcompleteexcision(tumour-freemargins)while performing the surgery.5,6 Recurrenceratesrangefrom0to7%withMohssurgery,andupto16%withwideexcision.7Owingtothepossibilityofthetumourextendingintosubcutaneoustissueand,rarely,metastasizing, cryosurgery and electrodesiccation andcurettagearegenerallynotrecommendedfortreatmentofAFX.1Regardlessoftreatment,however,allpatientsshouldfollowupwithin6monthstoensurethereisnolocalrecurrence.

Mr Prajapati is a third-year medical student at the University of Calgary in Alberta. Dr Barankin is a dermatologist in Toronto, Ont.

Competing interestsNone declared

references1.StadlerFJ,ScottGA,BrownMD.Malignantfibroustumors.Semin Cutan Med

Surg1998;17(2):141-52.2.Diaz-CascajoC,BorghiS,BonczkowitzM.Pigmentedatypicalfibroxanthoma.

Histopathology1998;33(6):537-41.3.AndersonPJ,McPhadenAR,RatcliffeRJ.Atypicalfibroxanthomaofthescalp.

Head Neck2001;23(5):399-403.4.FretzinDF,HelwigEB.Atypicalfibroxanthomaoftheskin.Aclinicopatholog-icalstudyof140cases.Cancer1973;31(6):1541-52.

5.SeavoltM,McCallM.Atypicalfibroxanthoma:reviewoftheliteratureandsummaryof13patientstreatedwithMohsmicrographicsurgery.Dermatol Surg2006;32(3):435-41.

6.GiuffridaTJ,KligoraCJ,GoldsteinGD.Localizedcutaneousmetastasesfromanatypicalfibroxanthoma.Dermatol Surg2004;30(12Pt2):1561-4.

7.HuetherMJ,ZitelliJA,BrodlandDG.Mohsmicrographicsurgeryforthetreatmentofspindlecelltumorsoftheskin.J Am Acad Dermatol2001;44(4):656-9.