Abstract
Lumbar epidural lipomatosis (LEL) is characterized by the abnormal accumulation of unencapsulated adipose tissue in the spinal epidural space. Symptomatic LEL occurs in middle aged and elderly patients, and it is most often seen in males. The purpose of this study was to elucidate the histopathological and cytogenetic characteristics of the epidural lipomatosis in patients with symptomatic LEL. Six patients undergoing decompressive spinal surgery (mean age, 69.4 years) were enrolled between 2013 and 2017. Three cases were steroid-induced and 3 cases were diagnosed as idiopathic LEL. We compared the differences in histological morphology between the subcutaneous fat tissue and epidural fat tissue in each patient. We also analyzed the karyotype of resected epidural lipomatous tissue using the G-band method. The epidural adipocytes were histologically more irregular and smaller compared with the subcutaneous adipocytes in all cases. The mean size of subcutaneous adipocytes and epidural adipocytes was 5,485.6 ± 2,584.1 µm2 and 2,705.4 ± 1,069.1 µm2, respectively. In cytogenetic analysis of the epidural adipocytes, loss of the Y chromosome (LOY) was found in all 6 cases. The mechanisms related to the development of LEL are not well understood. In this study, the size of the lipid component of epidural adipocytes was significantly smaller than that of subcutaneous adipocytes in LEL. Cytogenetically, LOY was frequently recognized. Although this may be an effect rather than a cause, LOY may be related to morphologic changes in and proliferation of adipocytes in LEL. LOY might partially contribute to the pathological mechanism or expression of LEL.