Dystrophic scrotal calcinosis originating from benign eccrine epithelial cysts.

Scrotal calcinosis has been classified as a form of idiopathic calcinosis cutis. However, the pathogenesis of the calcified nodules has not been fully elucidated: it is still unclear whether the condition is truly idiopathic, or the result of breakdown of calcified epithelial cysts. We describe a 29-year-old Japanese patient with scrotal calcinosis originating from epithelial cysts. Light microscopy revealed a large epithelial cyst containing von Kossa-positive material and several small dilated ductal structures beside the cyst. The epithelia of the cyst and ductal structures were connected, showing similar eccrine duct differentiation on immunohistochemical staining and electron microscopy. In the cyst lumen, calcium was present as needle-shaped crystals. The pathogenetic mechanism of calcium deposition seemed to be due to excessive production and discharge of matrical debris and sulphated mucopolysaccharides, which derived from luminal cells, and their accumulation in the lumina.