ANEURYSMAL CYST OF SOFT-TISSUE - REPORT OF A CASE WITH SERIAL MAGNETIC-RESONANCE-IMAGING AND BIOPSY

We report a case of an extraosseous aneurysmal cyst arising in the lef t retroclavicular soft tissue of a 29-year-old woman, A magnetic reson ance imaging (MRI) scan showed a solid lesion within soft tissue, abut ting the clavicle without bone involvement, An incisional biopsy was i nterpreted as showing osteoclast rich nodular fasciitis with prominent vascularity, A second MRI 5 months later showed intralesional cystic change with areas of increased signal on TB weighted images, still wit hout any bony defect, The lesion was excised, Histological examination revealed large vascular spaces lined focally by Want cells, The remai nder of the lesion was composed of an admixture of spindle cells and o steoclast-like giant cells. The histological and ultrastructural appea rance was that of an aneurysmal bone cyst; however, in view of the lac k of any bony involvement, a diagnosis of aneurysmal cyst of soft tiss ue was made, Primary aneurysmal cysts of soft tissue are rare; this is the third well-documented case in the literature, and the first to de scribe both the;MRI appearance and the histological evolution from a s olid to multiloculated lesion, Copyright (C) 1997 by W.B. Saunders Com pany.