Anterior Cutaneous Nerve Entrapment Syndrome in a 51-Year-Old Woman With Advanced Colon Cancer, Successfully Treated With Repeated Ultrasound-Guided Rectus Sheath Blocks: A Case Report.

BACKGROUND Anterior cutaneous nerve entrapment syndrome is an underrecognized cause of abdominal wall pain and may be overlooked, particularly in patients with advanced cancer, in whom abdominal pain is often attributed to malignancy-related causes. Failure to identify coexisting non-cancer-related pain mechanisms can result in inadequate pain control and functional decline. CASE REPORT A 51-year-old woman with advanced sigmoid colon cancer and peritoneal metastasis presented with severe movement-related abdominal pain that was refractory to high-dose opioid therapy. Although tumor lesions were present near the umbilicus, she reported minimal pain at rest, with marked exacerbation during sitting and ambulation. Physical examination revealed multiple localized tender points along the lateral borders of the rectus abdominis muscle and a positive Carnett's sign, suggesting abdominal wall pain. Based on these findings, anterior cutaneous nerve entrapment syndrome was suspected. Ultrasound-guided bilateral rectus sheath blocks were performed at the tender points, resulting in immediate pain relief. Although the initial analgesic effect was transient, repeated blocks led to sustained pain reduction beyond the expected duration of local anesthetic action, enabling recovery of mobility and activities of daily living. CONCLUSIONS This case shows that anterior cutaneous nerve entrapment syndrome can coexist with cancer-related pathology and is a treatable cause of refractory abdominal pain in patients with advanced cancer. Careful assessment of pain characteristics and physical examination, even in the presence of tumor lesions at the pain site, can facilitate recognition and treatment of non-cancer-related pain and improve functional outcomes and quality of life in palliative care settings.