Incision-Site Scalp Metastasis After Gross Total Resection of a Frontal Gliosarcoma: A Case Report of Probable Surgical Seeding

Gliosarcoma is a rare histological subtype of glioblastoma, IDH-wildtype, composed of malignant glial and sarcomatous components, with a higher propensity for extracranial dissemination than conventional glioblastoma.Metastasis to the scalp along the craniotomy incision is exceedingly rare.We report the case of a 43-year-old man who presented with a first generalized seizure and was found to have a right frontal necrotic, ring-enhancing mass.He underwent gross total resection, and histopathology showed a gliosarcoma with glial fibrillary acidic protein (GFAP)-positive glial and vimentin-positive mesenchymal components.He then received radiotherapy with concomitant and adjuvant temozolomide, and MRI at five months showed no recurrence.Nine months after surgery, a progressively enlarging subcutaneous nodule appeared along the previous incision.MRI showed an extracranial scalp mass overlying an intact bone flap, without intracranial continuity or intracranial recurrence.The lesion was excised, and histopathology showed a high-grade sarcomatoid tumor with diffuse expression of GFAP, vimentin, and p53, consistent with metastatic gliosarcoma.The patient's general condition subsequently deteriorated, and he died of intracranial progression six months after the diagnosis of the scalp metastasis.The location of the lesion strictly along the incision, the absence of intracranial recurrence, the identical histology, and the delayed onset all support iatrogenic seeding of tumor cells along the surgical tract.This report highlights the importance of meticulous tumor handling and wound protection during surgery, as well as careful examination of the scar during follow-up.