# Primary Intracranial Squamous Cell Carcinoma Arising from an Epidermoid Cyst: Successful Management with Subtotal Resection and Gamma Knife Radiosurgery in an Elderly Patient

## TL;DR

An elderly patient with a rare brain tumor was successfully treated with partial surgery and Gamma Knife radiation instead of aggressive therapy.

## Contribution

Gamma Knife radiosurgery is proposed as a safer alternative for elderly patients with rare brain tumors.

## Key findings

- Subtotal resection and Gamma Knife radiosurgery controlled the tumor for 18 months without severe side effects.
- Gamma Knife is a viable alternative for high-risk patients who cannot tolerate standard treatments.
- The approach preserved quality of life and systemic immune integrity.

## Abstract

Primary intracranial squamous cell carcinoma arising from a benign epidermoid cyst is an extremely rare and aggressive brain tumor. Conventional treatment involves extensive surgery and wide-field radiation, but this approach can be too dangerous for elderly or frail patients. We report the case of a 75-year-old woman with this diagnosis who could not undergo conventional aggressive therapy due to her poor health and the tumor’s proximity to critical brain structures. Instead, she received a partial removal of the tumor followed by Gamma Knife radiosurgery, a precise form of focused radiation. This tailored approach successfully controlled the cancer for 18 months without causing severe side effects. Our findings suggest that Gamma Knife radiosurgery can be an effective and safer alternative for high-risk patients who cannot tolerate standard intensive treatments.

Primary intracranial squamous cell carcinoma (SCC) arising from an epidermoid cyst is an exceptionally rare and aggressive malignancy with a dismal prognosis. Conventional management typically involves gross total resection followed by wide-field radiotherapy; however, this intensive approach is often unfeasible for elderly or frail patients. We present a case of primary intracranial SCC in a 75-year-old woman who presented with rapid cochleovestibular deterioration. Imaging revealed subtle enlargement of a long-standing cerebellopontine angle epidermoid cyst. Subtotal resection was performed to preserve critical neurovascular structures adherent to the infiltrative tumor. Given the patient’s poor performance status and the risk of toxicity from broad-field radiation, adjuvant Gamma Knife radiosurgery (GKS) was selected as a focal salvage modality. Despite the limited surgical margin, the patient has maintained a progression-free status with no radiographic evidence of disease progression for 18 months without neurological decline. This case highlights the diagnostic challenge of malignant transformation disguised by radiologic mimicry and demonstrates that GKS can serve as an effective and tolerable adjuvant strategy. We propose that for high-risk patients precluded from intensive multimodal therapy, focused stereotactic irradiation offers a viable alternative to secure local control while preserving quality of life and systemic immune integrity.