[Unusual "lipid cysts" in the acetabular labrum of patients with hip joint osteoarthrosis]

Diagnostic pathological examination of surgical specimens from patients with hip joint osteoarthrosis occasionally exhibits as yet undescribed pseudocysts consisting of folded granular membranes in necrotic or chondroid tissues. When stained with Sudan red, the content of these cysts indicates the presence of lipid substances. The presence of S100 protein-positive cells with intracytoplasmic fat vacuoles as well as such cells in the walls indicate that they develop from fat inclusions occurring in the chondroid cells of the labrum. Two different wall structures were detected by electron microscopy. The first type exhibited small walls of a granular material similar to the endoplasmic reticulum that surrounds intracytoplasmic fat globules. The second type consisted of broad layers of very tiny granules indicating a more advanced stage of the development of these cysts. The reason for the occurrence of these "chondrocytogenic lipid cysts" remains unknown-it may be assumed that they are due to mechanical labrum destruction that occurs in osteoarthrosis.