A Lip Lump: An Unexpected Histological Diagnosis of a Lip Schwannoma

Schwannomas are benign nerve sheath tumours arising from Schwann cells. They comprise 1% of all benign tumours. In the 2016 World Health Organisation Classification of Central Nervous System, they are classified as a tumour of the cranial and paraspinal nerves, Schwannoma 9560/0. A 23-year-old Caucasian lady presented with a seven-month history of a painless right upper lip lump. Examination revealed a small cystic 0.5 cm diameter lesion within the right upper lip. The clinical impression was that of a mucocele. Excision of the lip lesion was performed under local anaesthetic. Histological examination of the excised lesion demonstrated a circumscribed nodule consisting of spindle cells mixed with vascular spaces containing red blood cells and fibrin. Immunohistochemistry for S100 was strongly positive. The findings were consistent with that of a small benign schwannoma. The current consensus is for surgical excision of a conservative nature with no need for margins. If recurrence does occur one needs to consider whether complete enucleation was achieved or whether malignant transformation has occurred.