Imaging of pseudoneoplastic masses associated with allografts

The objective of this study is to describe the imaging features of non-neoplastic masses suspected of being tumor recurrences adjacent to allografts. The allografts were utilized for the treatment of various musculoskeletal tumors. We reviewed the medical records and imaging studies of 56 patients who were suspected of having recurrent tumors following surgical resection and allograft replacement treatment for a variety of musculoskeletal neoplasms. The imaging modalities included radiographs, CT, and MRI. There were 47 cases of recurrent tumors. All tumor recurrences were in the soft tissues of the surgical bed (41 patients), or in the native bone adjacent to the host/allograft junction (6 patients). None of the recurrences originated in the allografts. Nine patients suspected of having recurrences were discovered to have non-neoplastic masses. Five of these were very closely related to the allograft, wrapping around parts of the allograft, and the other 4 were in the surgical bed, 2 of which were abscesses and two were seromas. Most masses arising in the vicinity of allografts implanted following resection of musculoskeletal tumors represent recurrent neoplasms. A minority are reactive processes or abscesses or fluid collections. These ''pseudoneoplasms,'' specifically those closely related to the allografts, have specific imaging characteristics that help distinguish them from recurrent tumors. (orig.)