Keratoacanthoma, contentious

KA features:  symmetry; rounded base; stops at sweat glands; no desmoplasia; inflammatory reaction with PMN’s and eos; adenomatoid sweat coil transformation 

SCC features missing: pushing borders; acantholysis; follicular mucin; asymmetry; solid areas without maturation. 

Case 2767  12.2.21 (R. Carr) M 50 cheek nodule 4 weeks. 

I scored 7/32; RC 4.5/32 – i.e. equivocal.  Too much elastic entrapment for IFK/seb k.  Location and rapid growth suggest KA.  Uncertain final diagnosis.  Low-risk lesion not requiring long-term 2ry care follow-up. 

RC has stopped including elastic entrapment in his scoring system, except where  differential includes reactive pseudoepitheliomatous hyperplasia v's invasive lesion.