Mucinous adenocarcinoma presenting as adult colonic intussusception

Rationale: Colonic intussusception is a rare cause of intestinal obstruction in adults, and is frequently associated with an underlying malignancy. Mucinous adenocarcinoma (MAC) is an uncommon histological subtype of colorectal cancer, characterized by abundant extracellular mucin and unfavorable biological behaviors. However, its presentation as a lead point for an intussusception is rare. Here we describe a rare case of MAC causing colonic intussusception. Patient concerns: We describe the case of a 75-year-old woman with multiple comorbidities who presented with hematochezia, abdominal distension, intermittent colicky pain, and progressive weight loss. Diagnoses: Colonoscopy revealed a large intraluminal mass in the ascending colon, while contrast-enhanced computed tomography revealed ileocecal intussusception with ischemic features. Interventions: Emergency right hemicolectomy was performed. Histopathology confirmed a moderately differentiated MAC without lymph node metastasis. Molecular analysis revealed a p.Gly13Asp KRAS (KRAS proto-oncogene, GTPase; protein change: glycine to aspartate substitution at codon 13) mutation with microsatellite stability. Outcomes: The patient’s prolonged immobility due to dementia and prior hip fracture surgery likely contributed to chronic bowel hypomotility, potentially exacerbating symptoms. Lessons: This case presents an unusual occurrence of MAC causing adult colonic intussusception, highlighting how tumor biology may synergize with host-related factors such as immobility to accelerate clinical deterioration. Early recognition using endoscopy and computed tomography and timely surgical resection is essential to optimize outcomes.