A Queensland study has shown that two-thirds (67%) of excised keratacanthomas are in a histopathological stage of regression.

The analysis of 738 keratoacanthomas in the QSkin study suggests a strong potential for spontaneous resolution of many lesions.

Senior investigator Dr Magdalena Claeson, from the QIMR Berghofer Medical Research Institute and the University of Gothenburg, Sweden, told the limbic the intriguing tumours posed a clinical dilemma.

“We do not know yet why keratoacanthomas can resolve completely. It could be a sign of an immune response that is activated in the patient, usually after a few months. Keratoacanthoma on the other hand is classified as a variant of the more well-known SCC, a malignant tumour.”

“If we could understand the biological process behind the quickly developing and then regressing keratoacanthoma, this could help us develop better means to treat these, and possibly other similar tumours.”

The study, published in Acta Dermato-Venereologica, found the majority of keratocanthomas in men and women were located on the legs and feet (48%), arms and hands (33%), and less often on the trunk (12%) or head and neck (7%).

The median size of the tumours was largest on the legs and feet (10mm) compared to arms and hands (9mm), trunk (8mm) and head and neck (6.55mm).

Older people and men also had larger tumours.

“We do know that men with similar tumours – SCCs – present with larger tumours than women and that there is a tendency to delayed care-seeking among men. Possibly this is one of the reasons for our findings.”

“I would encourage all Australians with a new and/or growing skin lesion to go see their doctor, but I would especially like to encourage elderly men to seek care – do not wait too long. Even if keratoacanthomas do not metastasise, if the patients wait too long they can end up with a large tumour that is more complicated to excise than a small tumour,” she said.

The study noted most tumours (82%) were managed by excision in general practice.

Only 11% of tumours were referred to a dermatologist where they were more likely to be managed with curettage (42%), then excision (32%) or shave biopsy(28%).

Dr Claeson said skin tumours were unfortunately so abundant in Australia that GPs have to treat the majority of the tumours including keratoacanthomas.

However she said referrals for treatment to dermatologists and plastic surgeons may have been more common if the keratoacanthomas were more common on the face.

“Also, for keratoacanthomas there is usually no need for a wide local excision, unlike for melanoma. Wide excisions more often result in the need for skin grafts or surgical flaps, where specialist surgery may be required.”

Previous research from the cohort, reported in the limbic last year, identified keratoacanthoma risk factors including male gender, fair skin, freckles on the face at age 21 years, and a previous skin cancer removed.

The current study also showed that older people ≥60 years were slightly more likely to have multiple tumours (20%) than 50-59 year olds (13%) and <50 years (14%).