Pathology of synovial lipomatosis and its clinical significance

Synovial lipomatosis is a rare disorder of the synovium, commonly affecting the knee joint, resulting in joint pain, swelling, and effusion. The etiology of this condition still remains unclear.

This was a study done to evaluate the disease process in synovial lipomatosis, with respect to the clinical parameters and pathological features.

Case files of synovial lipomatosis diagnosed on histopathology between 2007 and 2009 were perused, to study the case history, and tissue sections were reviewed for the histomorphological changes.

Eight cases of synovial lipomatosis were diagnosed on histopathology from year 2007 to 2009, of which one occurred in the wrist joint and the rest were localized to the knee joint. Age ranged from one year to seventy-three years, with a male preponderance. Pain and swelling were major complaints. Three had a significant past history, one occurring post-trauma, one following chikungunya, and another with septic arthritis. Three of the cases had osteoarthritis. Body mass index was elevated in four cases and one case had protein energy malnutrition. On histopathological examination, all the cases showed villous proliferation of the synovium, with focal and diffuse infiltration by mature adipocytes. Four cases showed focal hyperplasia of the lining epithelium and five cases revealed variable fibrosis.

Synovial lipomatosis may mimic tumorous, lesion-like synovial lipoma or hemangioma and its distinct histomorphology helps in distinguishing it from these lesions. It possibly represents a secondary phenomenon following the degenerative process of articular disease of the joints.