204 The malignancy potential of porokeratosis: a single-center retrospective study

Porokeratosis (PK) is a rare group of keratinization disorders with an overall favorable prognosis. However, malignant transformation of PK to skin cancer has been reported in 6.9% to 11.6% of cases. This estimate is based on reviews of published cases, which introduces possible publication bias. We aimed to eliminate this potential bias and quantify the characteristics, risk factors, and malignancy potential of PK. A single-center retrospective chart review of patients with a diagnosis of PK was conducted. Out of 110 patients with histologically-confirmed PK, 6.4% to 16.4% demonstrated malignant transformation. A higher proportion of disseminated superficial actinic porokeratosis (DSAP) cases showed malignant transformation compared to porokeratosis of Mibelli (as high as 29.3% vs. 6.0%, respectively, p=.0016). Out of two cases of linear PK, both demonstrated malignant transformation. Exposures including immunosuppression, radiation therapy, phototherapy, and a personal history of skin cancer were not associated with increased risk of malignant transformation. Although the etiology of malignant transformation remains unclear, PKs are at risk for malignant transformation, and patients with DSAP and linear PK, in particular, should receive more long-term surveillance.