Solitary sclerotic fibroma of the skin: morphological characterization of the ‘plywood‐like pattern’

Sclerotic fibroma is an uncommon skin tumor. Rapini and Golitz reported 11 cases of solitary sclerotic fibromas in patients without Cowden's disease in 1989. We report a case of sclerotic fibroma that presented as an asymptomatic nodule in a 34-year-old Japanese man. Histopathological examination revealed typical features of sclerotic fibroma of the skin. Ultrastructural examination showed that spindle cells with myoid features had proliferated around the vasculature. They had segregated from the perivascular area by leaving the surrounding basal lamina, resulting in their phenotypical change to produce collagen accumulating in a concentrically lamellar fashion. We suggest a possible role of abnormal blood vessels and surrounding specific cells in the development of sclerotic fibroma.