Histopathological Features of Secondary Squamous Cell Carcinoma Around a Dental Implant in the Mandible After Chemoradiotherapy: A Case Report With a Clinicopathological Review.

Oral squamous cell carcinoma (OSCC) around a dental implant is a rare pathologic condition. This report describes a case of recurrent OSCC surrounding a dental implant, histopathologic findings, and a literature review of this condition. A 58-year-old Japanese woman underwent chemoradiotherapy for OSCC in the right lower gingiva, resulting in a complete response. Nine years after primary chemoradiotherapy, a dental implant was placed in her atrophic mandible. Three years later, an OSCC developed around the dental implant in the right lower premolar region. Marginal mandibulectomy was performed. Microscopic examination showed medullary invasion around the implant surface, suggesting that tumor infiltration of the bone was through the interface between the implant and bone. However, no downward invasion through the interface was evident. OSCC can develop around dental implants that are placed for oral rehabilitation after ablative surgery. Staging of OSCC and planning of surgical management should be carried out carefully, because implants placed adjacent to the OSCC can influence tumor invasion. A high degree of vigilance for OSCC is required during follow-up of patients with dental implants who have OSCC risk factors such as premalignant lesions. Detailed evaluation, including biopsy examination, is essential for distinguishing peri-implantitis from OSCC.