Bony and Cartilaginous Tissues in Lumbosacral Lipomas

It is well known that bony and cartilaginous tissues can be present in lumbosacral lipomas; however, the relationship between their presence and clinical features has not been demonstrated.

Five (10.4%) out of 48 patients had osteochondral tissues in lipomas. We retrospectively analyzed the clinical, neuroradiological, and histological findings of these patients.

Five (45.5%) of 11 patients with dorsal and transitional type lipomas had osteochondral tissues, while none with caudal and filar type lipomas had these tissues. Presurgical imaging demonstrated that the osteochondral tissue was located in a large subcutaneous lipoma dorsal to the bifid vertebral column. Histologically, mature bone with hematopoietic marrow and hyaline cartilage were observed in 3 and 2 patients, respectively.

The high incidence of association of osteochondral tissues with dorsal and transitional type lipomas is thought to be the result of primary neurulation failure with invasion of mesenchymal tissues. Caudal and filar type lipomas, resulting from secondary neurulation failure, thus did not have osteochondral tissue.