Membranocystic lesion in sclerosing lipogranuloma of the scrotum: an ultrastructural study.

Two cases of intrascrotal sclerosing lipogranuloma are reported in which affected adipose tissues showed peculiar membranocystic lesions (MCL) similar to the features described in Nasu-Hakola disease. On light microscopy, the MCL were seen in the degenerative fatty tissues and within multinucleated giant cells, which were positive for periodic acid-Schiff stain and resistant to diastase digestion. Ultrastructurally, two types of MCL were observed; one type was characterized by thick membranes composed of vesicular to minute tubular or fibrillar substructures, and the other type was characterized by thin membranes composed of only small numbers of tiny vesicles. The substructures in both types of MCL contained lipid droplets similar to those in the inner space. These results support the concept that the membranes in the MCL are derived from degenerated fat droplets.