Cancer proneness of linear porokeratosis may be explained by allelic loss.

Background: It is well known that porokeratosis, a genetically heterogeneous disorder characterized by the histopathological feature of the cornoid lamella, shows an increased proneness to develop carcinoma. On the other hand, a significant mechanism in the origin of many forms of cancer is loss of heterozygosity or allelic loss.

Objective: Because it has recently been proposed that linear porokeratosis may result from allelic loss, one might expect that linear porokeratosis is especially prone to malignant degeneration. In order to test this hypothesis, a review of case reports was performed.

Method: Cases of cancer-associated porokeratosis were collected from the European language literature and assigned to one of 5 different types [plaque type of Mibelli (PM); disseminated actinic superficial porokeratosis (DSAP); porokeratosis palmaris, plantaris et disseminata (PPPD); porokeratosis punctata palmaris et plantaris (PPPP); linear porokeratosis (LP)].

Results: Malignant or premalignant lesions were reported in 9 cases of PM, 15 cases of DSAP, 3 cases of PPPD, 1 case of PPPP and 21 cases of LP.

Conclusion: This analysis supports the view that among the various forms of porokeratosis, the linear type is particularly susceptible to malignant degeneration. Arguments are presented in favor of the assumption that the genetic mechanism of allelic loss giving rise to LP may represent an initial step in the development of cancer.