Schwannoma derived from lingual nerve occurring in floor of mouth.

A schwannoma is a benign tumor composed of schwann cells which forms on the periphery of nerves. We report a case of a schwannoma derived from a lingual nerve occurring in the floor of the mouth. The patient was a 27-year-old woman who presented with the complaint of a swelling in the floor of the mouth. It is difficult to distinguish a swelling from a sublingual gland tumor, cyst, or malignant tumor by MRI alone. Therefore, a biopsy and cytological examination were performed one week prior to surgery to determine whether the growth represented a malignancy. The results revealed a class II growth which was suspected to be a schwannoma. Intraoperatively, it became clear that the tumor and lingual nerve were inseparable, making excision of the nerve unavoidable. On the other hand, there was a clear border between the tumor and the sublingual gland, so it was possible to preserve the sublingual gland. In the postoperative pathological diagnosis, a definitive diagnosis was difficult based solely on H-E staining. Therefore, immunohistochemical staining was performed, resulting in a diagnosis of schwannoma. Currently, the patient is still being followed up. The results of this case indicate that preoperative aspiration biopsy cytology is useful in deciding the operative method to be employed.