Abstract

Background: Brain metastasis (BM) is observed in approximately 0.3–3.2% of cases involving metastatic colon cancer and is almost invariably associated with extracranial dissemination. The occurrence of isolated intracranial disease in the absence of systemic metastases is, therefore, exceedingly rare.

Case presentation: We report a 74 year-old female who presented with new-onset focal seizures 18 months after curative surgery for stage IIIC sigmoid adenocarcinoma. The 18Fluorine fluorodeoxyglucose positron emission tomography/computed tomography (18F- FDG PET/CT) scan revealed increased 18F-FDG uptake in an 18x19 mm hyperdense lesion located in the right temporal lobe, accompanied by a substantial edematous region in the surrounding area (SUV max:8.0) but no abnormal 18F-FDG accumulation elsewhere, confirming isolated BM. Brain Magnetic Resonance Imaging (MRI) revealed a 28x30 mm contrast-enhancing lesion in the right temporal lobe with vasogenic edema. The patient underwent gross-total resection followed by adjuvant stereotactic radiosurgery (SRS, 18 Gy single fraction). Histopathology showed metastatic moderately-differentiated colon adenocarcinoma (CK20+, CDX-2+, CK7+, P53+). Post-operative capecitabine plus bevacizumab was given for six cycles. At 12-month follow-up the patient remains disease-free on surveillance MRI and 18F-FDG PET/CT.

Conclusion: This case illustrates the diagnostic value of 18F-FDG PET/CT in excluding extracranial disease and supports an aggressive local-therapy strategy (surgery ± SRS) for solitary colon adenocarcinoma BM, which may confer prolonged survival.

Key words: colon cancer, solitary brain metastasis, 18F-FDG PET/CT.