Porokeratosis large skin lesions are susceptible to skin cancer development: histological and cytological explanation for the susceptibility.

Porokeratosis (PK), an autosomal dominant inherited skin disorder, is known to develop malignant skin tumors on its skin lesions. Our recent literature survey has revealed that large PK skin lesions are frequently a precursor of malignant changes. In the study, large and small PK skin lesions were investigated in terms of histological features of the epidermis and of the cellular DNA content of epidermal cells. Large PK lesions frequently showed hypertrophic epidermis with many mitotic cells, while small lesions usually presented atrophic epidermis without such mitotic cells. Abnormal cells, like those containing hyperchromatic, large, and/or irregularly shaped nuclei, were present in the epidermis of both large and small lesions with a preponderance in the former over the latter. DNA polyploidy was seen more frequently in large PK lesions than in small ones. DNA index values were significantly higher in large lesions than in small ones. The histological features and DNA ploidy abnormalities probably reflect the higher proliferation and the greater potential for malignant changes of large PK skin lesions. Our study helps to explain the clinical evidence that large PK skin lesions are frequently a precursor of malignant skin tumors.