Aims: To study the histological features of abortive keratoacanthoma, a variant that has only recently been recognised.
Methods: A key word search of the database of our pathology practice was carried out for all keratoacanthomas (KAs) reported by one author (DW) over a 14-month period. These cases were then sorted into histological subtypes by age in decades.
Results: A total of 3465 cases of KA were reported over this period, of which 582 (16.8%) were of the so-called abortive type. Abortive KAs are characterised by rapid growth and subsequent lichenoid regression at an early stage in their evolution. Lichenoid changes extend for a variable distance beyond the lesion.
Conclusions: Abortive KA is a hitherto unrecognised variant of KA which may be misdiagnosed as squamous cell carcinoma despite its distinctive features. Lichenoid regression, rather than terminal differentiation, is the main mechanism of its involution.