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Toronto Notes 2019 Malignant Skin Tumours Dermatology D35 SQUAMOUS CELL CARCINOMA
Clinical Presentation
• hyperkeratoticindurated,pink/red/skin-colouredpapule/plaque/nodulewithsurfacescale/crust± ulceration
• morerapidenlargementthanBCC
• exophytic(growsoutward),maypresentasacutaneoushorn
• sites:face,ears,scalp,forearms,dorsumofhands
Pathophysiology
• malignantneoplasmofkeratinocytes(primarilyverticalgrowth)
• predisposingfactorsinclude:UVradiation,PUVA,ionizingradiationtherapy/exposure,chemical
carcinogens (such as arsenic, tar, and nitrogen mustards), HPV 16, 18, immunosuppression
• mayoccurinpreviousscar(SCCmorecommonlythanBCC)
Epidemiology
• secondmostcommontypeofcutaneousneoplasm
• primarilyonsun-exposedskinintheelderly,M>F,skinphototypesIandII,chronicsunexposure
• inorgantransplantrecipients,SCCismostcommoncutaneousmalignancy,withincreasedmortalityas
compared to non-immunocompromised population
Differential Diagnosis
• benign:nummulareczema,psoriasis,irritatedseborrheickeratosis • malignant:keratoacanthoma,Bowen’sdisease,BCC
Management
• surgicalexcisionwithprimaryclosure,skinflapsorgrafting • Mohssurgery
• lifelongfollow-up(moreaggressivetreatmentthanBCC)
• radiationtherapy
Prognosis
• goodprognosticfactors:earlytreatment,negativemargins,andsmallsizeoflesion
• SCCsthatarisefromAKmetastasizelessfrequently(~1%)thanotherSCCsarisingdenovoinold
burns (2-5% of cases)
• overallcontrolis75%over5yr,5-10%metastasize
• metastasisratesarehigherifdiameter>2cm,depth>4mm,recurrent,involvementofbone/muscle/
nerve, location on scalp/ears/nose/lips, immunosuppressed, caused by arsenic ingestion, or tumour arose from scar/chronic ulcer/burn/genital tract/sinus tract
KERATOACANTHOMA
Clinical Presentation
• rapidlygrowing,firm,dome-shaped,erythematousorskin-colourednodulewithcentralkeratin-filled crater, resembling an erupting volcano
• mayspontaneouslyregresswithinayear,leavingascar
• sites:sun-exposedskin
Pathophysiology
• epithelialneoplasmwithatypicalkeratinocytesinepidermis • lowgradevariantofSCC
Etiology
• HPV,UVradiation,chemicalcarcinogens(tar,mineraloil)
Epidemiology
• >50yr,rare<20yr
Differential Diagnosis
• treatasSCCuntilprovenotherwise
• hypertrophicsolarkeratosis,verrucavulgaris
Management
• surgicalexcisionorsaucerization(shavebiopsy)followedbyelectrodesiccationofthebase,treated similarly to SCC
• intralesionalmethotrexateinjection