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Background: To investigate the clinicopathological features of six cases of soft tissue recurrent ameloblastoma
and explore the role of increased aggressive biological behavior in the recurrences and treatment of this type of
ameloblastomas.
Material and Methods: In this study, we retrospectively reviewed recurrent ameloblastomas during a 15-year period; six cases were diagnosed as soft tissue recurrent ameloblastoma. The clinical, radiographic, cytological and
immunohistochemical records of these six cases were investigated and analyzed.
Results: All the six soft tissue recurrent ameloblastomas occurred after radical bone resection, and were located
in the adjacent soft tissues around the osteotomy regions. In Case 4, the patient developed pulmonary metastasis,
extensive skull-base infiltration and cytological malignancy after multiple recurrences and malignant transformation was diagnosed. In the other five cases, although there were no cytological signs are sufficient to justify
an ameloblastoma as malignant, some malignant features were observed. In Case 1, the tumor showed moderate
atypical hyperplasia and the Ki-67 staining percentage was 40% positive, which are strongly suggestive of potential malignance. In Case 5, the patient developed a second soft tissue recurrence in the parapharyngeal region
and later died of tumor-related complications. All the remaining three patients showed cytology atypia of varying
degrees and high expression of PCNA or Ki-67, which confirmed active cell proliferation.
Conclusions: Increased aggressiveness is an important factor of soft tissue recurrence. An intraoperative rapid
pathological examination and more radical treatment are suggested for these cases.
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