A Case of Follicular Dendritic Cell Sarcoma of the Palatine Tonsil That Developed as a Radiation-Induced Sarcoma.

Follicular dendritic cell sarcoma is a rare malignant tumor originating from follicular dendritic cells. We present the first report of such a sarcoma of the palatine tonsils that developed as a radiation-induced sarcoma. A 78-year-old man, who had undergone chemoradiotherapy for hypopharyngeal and esophageal cancer 7 years prior, presented with discomfort during swallowing. Endoscopic pharyngeal examination revealed a tumor in the right palatine tonsil which was histopathologically diagnosed as a follicular dendritic cell sarcoma. The tumor also met the diagnostic criteria for radiation-induced sarcoma. Positron emission tomography/computed tomography revealed abnormal uptake in the right palatine tonsil and bilateral cervical lymph nodes; no distant metastases were detected. The patient underwent tumor resection using the mandibular swing approach, pharyngeal reconstruction using an anterolateral thigh flap, bilateral neck lymph node dissection, and tracheostomy. Postoperative radiotherapy was not administered because of previous irradiation; however, no apparent recurrence or metastasis was observed 4 years after surgery. Follicular dendritic cell sarcoma can develop over an extended period after previous irradiation. Extended resection with a negative margin may be pivotal in treating follicular dendritic cell sarcoma when postoperative radiotherapy cannot be administered.