Imaging of pseudoneoplastic masses associated with allografts

Objective: 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. Materials and methods: 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. Results: 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. Conclusion: 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.