Brain Metastasis From Anal Canal Squamous Cell Carcinoma: A Rare Case Report and Systematic Review.

Anal canal squamous cell carcinoma (ACSCC) is a rare malignancy, accounting for approximately 2% of all colorectal cancers. Brain metastases originating from this primary site are exceedingly uncommon and scarcely documented. The aim of this study is to review the literature-reported cases of brain metastases from ACSCC and to supplement this analysis with the description of a clinical case. A systematic review of the literature was conducted in accordance with PRISMA guidelines to identify published cases of brain metastases from ACSCC. The clinical and therapeutic features of these cases were analyzed. In addition, we present a rare case of a 74-year-old woman with a primary diagnosis of HPV-negative ACSCC with an isolated brain metastasis occurring 20 months after completion of definitive chemoradiotherapy. She underwent craniotomy with gross total resection of the mass and adjuvant stereotactic radiotherapy to the tumor bed. Overall, 4 papers were included. Prognosis following cerebral dissemination is generally poor, ranged from 3 months to 8 years. Management is predominantly palliative, with the goal of symptom relief. But recent advances in therapeutic strategies are contributing to improved long-term survival in these patients. Concerning our case report, a personalized approach was adopted. Six months after neurosurgery and adjuvant stereotactic radiotherapy, the patient was in good general condition with no new or progressive neurological symptoms, indicating effective control of cerebral disease. The patient is currently alive and receiving active treatment. This systematic review highlights the importance of prompt brain metastasis diagnosis and of a multimodal treatment approach--including surgery, radiotherapy and systemic therapy--to significantly enhance both prognosis and quality of life in affected patients. Clarifying biological pathways is essential for developing targeted therapies and advancing precision oncology in ACSCC. A multinational approach could help address this issue and potentially determine if treatment intensification is necessary.