Extra-digital glomus tumour of the forehead: a case report of a solitary solid histopathologic subtype

Abstract

Background: Glomus tumours (GT) are benign neoplasms that develop from neuro-myoarterial structures known as “glomus bodies” involved in temperature and blood pressure control. GT rarely occur in the head and neck region, and the specific location of the glomus tumour on the forehead is even more uncommon. Case presentation: We report the case of a 36-year-old female who presented with painless swelling on the forehead of one year duration with a progressive increase in size. Physical examination showed a small forehead swelling with an initial clinical diagnosis of a sebaceous cyst. The patient had local excision of forehead swelling which was submitted for histopathologic examination. Discussion: The initial histological differential diagnosis included glomus tumour, benign skin adnexal tumour and PEComa. The formalin-fixed-paraffin embedded tissue blocks of the lesion were then subjected to immunohistochemical analysis. The tumour cells were negative for cytokeratin and positive for SMA and S100. Based on the morphology and immunohistochemical staining characteristics of the tumour cells, a diagnosis of glomus tumour was made. Conclusion: Glomus tumour occurring on the forehead is uncommon. Therefore, a high index of suspicion is needed for diagnosis. Immunohistochemistry may be needed to confirm the diagnosis and rule out other close differential diagnoses.