Extracranial meningioma: a case of a rare tumour of the scalp

Extracranial meningiomas of the scalp are rare, comprising less than 2% of all meningiomas. We present a case of a woman in her 50s with a scalp soft tissue mass initially suspected to be a lipoma or sebaceous cyst, ultimately revealing an extracranial meningioma. Microscopy revealed rounded tumour cells forming small syncytial groups dispersed in abundant adipose tissue, with no connection to the intracranial compartment. Immunohistochemistry of tumour cells demonstrated positivity for Vimentin, S100, EMA, CD56, SMA, and PR, with negativity for cytokeratins amongst other markers. EPIC methylation array and copy number analysis identified loss of chromosome 22 supporting the diagnosis. The absence of mitoses, necrosis, and no intracranial connection confirmed an extracranial meningioma of the scalp. Overall, this case highlights the importance of molecular testing in diagnosing an unexpected, rare, histologically challenging soft tissue lesion.